Practical position-based quantum cryptography
NASA Astrophysics Data System (ADS)
Chakraborty, Kaushik; Leverrier, Anthony
2015-11-01
We study a general family of quantum protocols for position verification and present a class of attacks based on the Clifford hierarchy. These attacks outperform current strategies based on port-based teleportation for a large class of practical protocols. We then introduce the interleaved product protocol, a scheme for position verification involving only the preparation and measurement of single qubit states for which the best available attacks have a complexity exponential in the number of classical bits transmitted.
Loss-tolerant position-based quantum cryptography
NASA Astrophysics Data System (ADS)
Qi, Bing; Siopsis, George
2015-04-01
Position-based quantum cryptography (PBQC) allows a party to use its geographical location as its only credential to implement various cryptographic protocols. Such a protocol may lead to important applications in practice. Although it has been shown that any PBQC protocol is breakable if the adversaries pre-share an arbitrarily large entangled state, the security of PBQC in the bounded-quantum-storage model is still an open question. In this paper, we study the performance of various PBQC protocols over a lossy channel under the assumption that no entanglement is pre-shared between adversaries. By introducing the decoy state idea, we show that an extended Bennett-Brassard-1984-type PBQC protocol implemented with a weak coherent source and realistic single-photon detectors can tolerate an overall loss (including both the channel loss and the detection efficiency) of 13 dB if the intrinsic quantum bit error rate is 1%. We also study a few continuous variable PBQC protocols and show that they suffer from a 3-dB loss limitation.
Unconditionally secure commitment in position-based quantum cryptography.
Nadeem, Muhammad
2014-01-01
A new commitment scheme based on position-verification and non-local quantum correlations is presented here for the first time in literature. The only credential for unconditional security is the position of committer and non-local correlations generated; neither receiver has any pre-shared data with the committer nor does receiver require trusted and authenticated quantum/classical channels between him and the committer. In the proposed scheme, receiver trusts the commitment only if the scheme itself verifies position of the committer and validates her commitment through non-local quantum correlations in a single round. The position-based commitment scheme bounds committer to reveal valid commitment within allocated time and guarantees that the receiver will not be able to get information about commitment unless committer reveals. The scheme works for the commitment of both bits and qubits and is equally secure against committer/receiver as well as against any third party who may have interests in destroying the commitment. Our proposed scheme is unconditionally secure in general and evades Mayers and Lo-Chau attacks in particular. PMID:25346509
Insecurity of position-based quantum-cryptography protocols against entanglement attacks
NASA Astrophysics Data System (ADS)
Lau, Hoi-Kwan; Lo, Hoi-Kwong
2011-01-01
Recently, position-based quantum cryptography has been claimed to be unconditionally secure. On the contrary, here we show that the existing proposals for position-based quantum cryptography are, in fact, insecure if entanglement is shared among two adversaries. Specifically, we demonstrate how the adversaries can incorporate ideas of quantum teleportation and quantum secret sharing to compromise the security with certainty. The common flaw to all current protocols is that the Pauli operators always map a codeword to a codeword (up to an irrelevant overall phase). We propose a modified scheme lacking this property in which the same cheating strategy used to undermine the previous protocols can succeed with a rate of at most 85%. We prove the modified protocol is secure when the shared quantum resource between the adversaries is a two- or three-level system.
Insecurity of position-based quantum-cryptography protocols against entanglement attacks
Lau, Hoi-Kwan; Lo, Hoi-Kwong
2011-01-15
Recently, position-based quantum cryptography has been claimed to be unconditionally secure. On the contrary, here we show that the existing proposals for position-based quantum cryptography are, in fact, insecure if entanglement is shared among two adversaries. Specifically, we demonstrate how the adversaries can incorporate ideas of quantum teleportation and quantum secret sharing to compromise the security with certainty. The common flaw to all current protocols is that the Pauli operators always map a codeword to a codeword (up to an irrelevant overall phase). We propose a modified scheme lacking this property in which the same cheating strategy used to undermine the previous protocols can succeed with a rate of at most 85%. We prove the modified protocol is secure when the shared quantum resource between the adversaries is a two- or three-level system.
NASA Astrophysics Data System (ADS)
Bruß, D.; Meyer, T.
The Greek words "kryptos" ≡ "hidden" and "logos" ≡ "word" are the etymological sources for "cryptology," the science of secure communication. Within cryptology, one distinguishes cryptography (or "code-making") and cryptanalysis (or "code-breaking"). The aim of cryptography is to ensure secret or "secure" communication between a sender, traditionally called Alice, and a receiver, called Bob. The encryption and decryption of a so-called plain text into a cipher text and back is achieved using a certain key (not necessarily the same for Alice and Bob), as illustrated in Fig. 1. Here, "secure" means that an eavesdropper, called Eve, has no information on the message. In this chapter we will show that in classical cryptography (using classical signals), security relies on the assumed difficulty to solve certain mathematical tasks, whereas in quantum cryptography (using quantum signals), security arises from the laws of quantum physics.
Threshold quantum cryptography
Tokunaga, Yuuki; Okamoto, Tatsuaki; Imoto, Nobuyuki
2005-01-01
We present the concept of threshold collaborative unitary transformation or threshold quantum cryptography, which is a kind of quantum version of threshold cryptography. Threshold quantum cryptography states that classical shared secrets are distributed to several parties and a subset of them, whose number is greater than a threshold, collaborates to compute a quantum cryptographic function, while keeping each share secretly inside each party. The shared secrets are reusable if no cheating is detected. As a concrete example of this concept, we show a distributed protocol (with threshold) of conjugate coding.
Quantum Cryptography Without Quantum Uncertainties
NASA Astrophysics Data System (ADS)
Durt, Thomas
2002-06-01
Quantum cryptography aims at transmitting a random key in such a way that the presence of a spy eavesdropping the communication would be revealed by disturbances in the transmission of the message. In standard quantum cryptography, this unavoidable disturbance is a consequence of the uncertainty principle of Heisenberg. We propose in this paper to replace quantum uncertainties by generalised, technological uncertainties, and discuss the realisability of such an idea. The proposed protocol can be considered as a simplification, but also as a generalisation of the standard quantum cryptographic protocols.
Relativistic quantum cryptography
NASA Astrophysics Data System (ADS)
Molotkov, S. N.; Nazin, S. S.
2003-07-01
The problem of unconditional security of quantum cryptography (i.e. the security which is guaranteed by the fundamental laws of nature rather than by technical limitations) is one of the central points in quantum information theory. We propose a relativistic quantum cryptosystem and prove its unconditional security against any eavesdropping attempts. Relativistitic causality arguments allow to demonstrate the security of the system in a simple way. Since the proposed protocol does not empoly collective measurements and quantum codes, the cryptosystem can be experimentally realized with the present state-of-art in fiber optics technologies. The proposed cryptosystem employs only the individual measurements and classical codes and, in addition, the key distribution problem allows to postpone the choice of the state encoding scheme until after the states are already received instead of choosing it before sending the states into the communication channel (i.e. to employ a sort of "antedate" coding).
Relativistic quantum cryptography
Molotkov, S. N.
2011-03-15
A new protocol of quantum key distribution is proposed to transmit keys through free space. Along with quantum-mechanical restrictions on the discernibility of nonorthogonal quantum states, the protocol uses additional restrictions imposed by special relativity theory. Unlike all existing quantum key distribution protocols, this protocol ensures key secrecy for a not strictly one-photon source of quantum states and an arbitrary length of a quantum communication channel.
NASA Astrophysics Data System (ADS)
Salih, Hatim
2016-05-01
The phenomenon of quantum erasure has long intrigued physicists, but has surprisingly found limited practical application. Here, we propose a protocol for quantum key distribution (QKD) based on quantum erasure, promising inherent security against detector attacks. We particularly demonstrate its security against a powerful detector-blinding attack.
Secure communications using quantum cryptography
Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.
1997-08-01
The secure distribution of the secret random bit sequences known as {open_quotes}key{close_quotes} material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over {open_quotes}open{close_quotes} multi-km node-to-node optical fiber communications links is possible. We have also constructed a quantum key distribution system for free-space, line-of-sight transmission using single-photon polarization states, which is currently undergoing laboratory testing. 7 figs.
Secure communications using quantum cryptography
NASA Astrophysics Data System (ADS)
Hughes, Richard J.; Buttler, William T.; Kwiat, Paul G.; Luther, Gabriel G.; Morgan, George L.; Nordholt, Jane E.; Peterson, C. Glen; Simmons, Charles M.
1997-07-01
The secure distribution of the secret random bit sequences known as `key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions: Heisenburg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single- photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over `open' multi-km node-to-node optical fiber communications links is possible.
Cryptography, quantum computation and trapped ions
Hughes, Richard J.
1998-03-01
The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.
Quantum cryptography over underground optical fibers
Hughes, R.J.; Luther, G.G.; Morgan, G.L.; Peterson, C.G.; Simmons, C.
1996-05-01
Quantum cryptography is an emerging technology in which two parties may simultaneously generated shared, secret cryptographic key material using the transmission of quantum states of light whose security is based on the inviolability of the laws of quantum mechanics. An adversary can neither successfully tap the key transmissions, nor evade detection, owing to Heisenberg`s uncertainty principle. In this paper the authors describe the theory of quantum cryptography, and the most recent results from their experimental system with which they are generating key material over 14-km of underground optical fiber. These results show that optical-fiber based quantum cryptography could allow secure, real-time key generation over ``open`` multi-km node-to-node optical fiber communications links between secure ``islands.``
The organization and traffic engineering of a quantum cryptography network
NASA Astrophysics Data System (ADS)
Zhao, YuKang; Zhao, MeiSheng; Zhao, Yong; Chen, ZengBing
2012-09-01
How many users can a quantum cryptography network support when certain services are demanded? The answer to this question depends on three factors: the speed of quantum key distribution, the organization and traffic engineering of the quantum cryptography network, and the engineering of services. In this article we focus on the second factor which is lacked in the literature to our knowledge but in urgent need for constructing an optimized large-scale quantum cryptography network. In order to provide an overall understanding about a quantum cryptography network, we also briefly introduce the characteristics of quantum cryptography and service engineering.
Quantum cryptography on optical fiber networks
NASA Astrophysics Data System (ADS)
Townsend, Paul D.
1998-07-01
Quantum cryptography exploits the fact that an unknown quantum state cannot be accurately copied or measured without disturbance. By using such elementary quantum states to represent binary information it is possible, therefore, to construct communication systems with verifiable levels of security that are 'guaranteed' by fundamental quantum mechanical laws. This paper describes recent progress at BT Laboratories in the development of practical optical fiber- based quantum cryptography system. These developments include interferometric systems operating in the 1.3 micrometers - wavelength fiber transparency window over point-to-point links up to approximately 50km in length and on multi-user passive optical networks. We describe how this technology performs on fiber links installed in BT's public network and discuss issues such as cross-talk with conventional data channels propagating at different wavelengths in the same fiber.
Quantum three-pass cryptography protocol
NASA Astrophysics Data System (ADS)
Yang, Li; Wu, Ling-An; Liu, Songhao
2002-09-01
We present a new kind of quantum cryptography protocol based on Shamir's three-pass protocol of classical cryptography, which allows the transmission of qubits directly and secretly via the aid of an unjammable classical channel. In this protocol we implement the encryption and decryption transformations via rotations on the Poincare sphere of the photons polarization parameters. The key technique is that Bob's encryption rotation must be commutative with Alice s decryption rotation; this means that the axes of these two rotations must be parallel. We also present a security analysis of the protocol under a man-in-the-middle attack.
Conditional efficient multiuser quantum cryptography network
NASA Astrophysics Data System (ADS)
Xue, Peng; Li, Chuan-Feng; Guo, Guang-Can
2002-02-01
We propose a conditional quantum key distribution scheme with three nonorthogonal states. Combined with the idea presented by Lo et al. (H.-K. Lo, H. F. Chau, and M. Ardehali, e-print arXiv: quant-ph/0011056), the efficiency of this scheme is increased to tend to 100%. Also, such a refined data analysis guarantees the security of our scheme against the most general eavesdropping strategy. Then, based on the scheme, we present a quantum cryptography network with the addition of a device called ``space optical switch.'' Moreover, we give out a realization of a quantum random number generator. Thus, a feasible experimental scheme of this efficient quantum cryptography network is completely given.
Quantum cryptography on multiuser optical fibre networks
NASA Astrophysics Data System (ADS)
Townsend, Paul D.
1997-01-01
To establish a secure communication channel, it is necessary to distribute between two users a key which allows safe encryption and decryption of messages. But because decryption is a simple task for any key holder, it is crucial that the key remains secret during distribution. Secrecy cannot be guaranteed if distribution occurs on the basis of classical physical mechanisms, as it is impossible to know whether the key has been intercepted during transmission. Quantum cryptography1-3 provides a fundamental solution to this problem. When quantum-mechanical processes are used to establish the key, any eavesdropping during transmission leads to an unavoidable and detectable disturbance in the received key information. Quantum cryptography has been demonstrated using standard telecommunication fibres linking single pairs of users4-8, but practical implementations will require communication networks with many users9. Here I introduce a practical scheme for multi-user quantum cryptography, and demonstrate its operation on an optical fibre network. The scheme enables a single controller on the network to establish, and regularly update, a distinct secret key with each network user. These keys can then be used to securely encrypt conventional data transmissions that are broadcast on the network.
Quantum discord as a resource for quantum cryptography.
Pirandola, Stefano
2014-01-01
Quantum discord is the minimal bipartite resource which is needed for a secure quantum key distribution, being a cryptographic primitive equivalent to non-orthogonality. Its role becomes crucial in device-dependent quantum cryptography, where the presence of preparation and detection noise (inaccessible to all parties) may be so strong to prevent the distribution and distillation of entanglement. The necessity of entanglement is re-affirmed in the stronger scenario of device-independent quantum cryptography, where all sources of noise are ascribed to the eavesdropper. PMID:25378231
FREE-SPACE QUANTUM CRYPTOGRAPHY IN DAYLIGHT
Hughes, R.J.; Buttler, W.T.
2000-01-01
Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.
Entanglement-Based Quantum Cryptography and Quantum Communication
NASA Astrophysics Data System (ADS)
Zeilinger, Anton
2007-03-01
Quantum entanglement, to Erwin Schroedinger the essential feature of quantum mechanics, has become a central resource in various quantum communication protocols including quantum cryptography and quantum teleportation. From a fundamental point of view what is exploited in these experiments is the very fact which led Schroedinger to his statement namely that in entangled states joint properties of the entangled systems may be well defined while the individual subsystems may carry no information at all. In entanglement-based quantum cryptography it leads to the most elegant possible solution of the classic key distribution problem. It implies that the key comes into existence at spatially distant location at the same time and does not need to be transported. A number recent developments include for example highly efficient, robust and stable sources of entangled photons with a broad bandwidth of desired features. Also, entanglement-based quantum cryptography is successfully joining other methods in the work towards demonstrating quantum key distribution networks. Along that line recently decoy-state quantum cryptography over a distance of 144 km between two Canary Islands was demonstrated successfully. Such experiments also open up the possibility of quantum communication on a really large scale using LEO satellites. Another important possible future branch of quantum communication involves quantum repeaters in order to cover larger distances with entangled states. Recently the connection of two fully independent lasers in an entanglement swapping experiment did demonstrate that the timing control of such systems on a femtosecond time scale is possible. A related development includes recent demonstrations of all-optical one-way quantum computation schemes with the extremely short cycle time of only 100 nanoseconds.
Security of counterfactual quantum cryptography
Yin Zhenqiang; Li Hongwei; Chen Wei; Han Zhengfu; Guo Guangcan
2010-10-15
Recently, a 'counterfactual' quantum-key-distribution scheme was proposed by T.-G. Noh [Phys. Rev. Lett. 103, 230501 (2009)]. In this scheme, two legitimate distant peers may share secret keys even when the information carriers are not traveled in the quantum channel. We find that this protocol is equivalent to an entanglement distillation protocol. According to this equivalence, a strict security proof and the asymptotic key bit rate are both obtained when a perfect single-photon source is applied and a Trojan horse attack can be detected. We also find that the security of this scheme is strongly related to not only the bit error rate but also the yields of photons. And our security proof may shed light on the security of other two-way protocols.
Free-space quantum cryptography
Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.; Lamoreaux, S.K.; Morgan, G.L.; Nordholt, J.E.; Peterson, C.G.
1998-12-31
An experimental free-space quantum key distribution (QKD) system has been tested over an outdoor optical path of {approximately}1 km under nighttime conditions at Los Alamos National Laboratory. This system employs the Bennett 92 protocol; here the authors give a brief overview of this protocol, and describe the experimental implementation of it. An analysis of the system efficiency is presented, as well as a description of the error detection protocol, which employs a two-dimensional parity check scheme. Finally, the susceptibility of this system to eavesdropping by various techniques is determined. Possible applications include the rekeying of satellites in low earth orbit.
Twenty Seven Years of Quantum Cryptography!
NASA Astrophysics Data System (ADS)
Hughes, Richard
2011-03-01
One of the fundamental goals of cryptographic research is to minimize the assumptions underlying the protocols that enable secure communications between pairs or groups of users. In 1984, building on earlier research by Stephen Wiesner, Charles Bennett and Gilles Brassard showed how quantum physics could be harnessed to provide information-theoretic security for protocols such as the distribution of cryptographic keys, which enables two parties to secure their conventional communications. Bennett and Brassard and colleagues performed a proof-of-principle quantum key distribution (QKD) experiment with single-photon quantum state transmission over a 32-cm air path in 1991. This seminal experiment led other researchers to explore QKD in optical fibers and over line-of-sight outdoor atmospheric paths (``free-space''), resulting in dramatic increases in range, bit rate and security. These advances have been enabled by improvements in sources and single-photon detectors. Also in 1991 Artur Ekert showed how the security of QKD could be related to quantum entanglement. This insight led to a deeper understanding and proof of QKD security with practical sources and detectors in the presence of transmission loss and channel noise. Today, QKD has been implemented over ranges much greater than 100km in both fiber and free-space, multi-node network testbeds have been demonstrated, and satellite-based QKD is under study in several countries. ``Quantum hacking'' researchers have shown the importance of extending security considerations to the classical devices that produce and detect the photon quantum states. New quantum cryptographic protocols such as secure identification have been proposed, and others such as quantum secret splitting have been demonstrated. It is now possible to envision quantum cryptography providing a more secure alternative to present-day cryptographic methods for many secure communications functions. My talk will survey these remarkable developments.
PREFACE: Quantum Information, Communication, Computation and Cryptography
NASA Astrophysics Data System (ADS)
Benatti, F.; Fannes, M.; Floreanini, R.; Petritis, D.
2007-07-01
The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12-23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy-Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable
Strong connections between quantum encodings, nonlocality, and quantum cryptography
NASA Astrophysics Data System (ADS)
Sikora, Jamie; Chailloux, André; Kerenidis, Iordanis
2014-02-01
Encoding information in quantum systems can offer surprising advantages but at the same time there are limitations that arise from the fact that measuring an observable may disturb the state of the quantum system. In our work, we provide an in-depth analysis of a simple question: What happens when we perform two measurements sequentially on the same quantum system? This question touches upon some fundamental properties of quantum mechanics, namely the uncertainty principle and the complementarity of quantum measurements. Our results have interesting consequences, for example, they can provide a simple proof of the optimal quantum strategy in the famous Clauser-Horne-Shimony-Holt game. Moreover, we show that the way information is encoded in quantum systems can provide a different perspective in understanding other fundamental aspects of quantum information, like nonlocality and quantum cryptography. We prove some strong equivalences between these notions and provide a number of applications in all areas.
On the complexity of search for keys in quantum cryptography
NASA Astrophysics Data System (ADS)
Molotkov, S. N.
2016-03-01
The trace distance is used as a security criterion in proofs of security of keys in quantum cryptography. Some authors doubted that this criterion can be reduced to criteria used in classical cryptography. The following question has been answered in this work. Let a quantum cryptography system provide an ɛ-secure key such that ½‖ρ XE - ρ U ⊗ ρ E ‖1 < ɛ, which will be repeatedly used in classical encryption algorithms. To what extent does the ɛ-secure key reduce the number of search steps (guesswork) as compared to the use of ideal keys? A direct relation has been demonstrated between the complexity of the complete consideration of keys, which is one of the main security criteria in classical systems, and the trace distance used in quantum cryptography. Bounds for the minimum and maximum numbers of search steps for the determination of the actual key have been presented.
Proposal for founding mistrustful quantum cryptography on coin tossing
Kent, Adrian
2003-07-01
A significant branch of classical cryptography deals with the problems which arise when mistrustful parties need to generate, process, or exchange information. As Kilian showed a while ago, mistrustful classical cryptography can be founded on a single protocol, oblivious transfer, from which general secure multiparty computations can be built. The scope of mistrustful quantum cryptography is limited by no-go theorems, which rule out, inter alia, unconditionally secure quantum protocols for oblivious transfer or general secure two-party computations. These theorems apply even to protocols which take relativistic signaling constraints into account. The best that can be hoped for, in general, are quantum protocols which are computationally secure against quantum attack. Here a method is described for building a classically certified bit commitment, and hence every other mistrustful cryptographic task, from a secure coin-tossing protocol. No security proof is attempted, but reasons are sketched why these protocols might resist quantum computational attack.
Analysis of limiting information characteristics of quantum-cryptography protocols
Sych, D V; Grishanin, Boris A; Zadkov, Viktor N
2005-01-31
The problem of increasing the critical error rate of quantum-cryptography protocols by varying a set of letters in a quantum alphabet for space of a fixed dimensionality is studied. Quantum alphabets forming regular polyhedra on the Bloch sphere and the continual alphabet equally including all the quantum states are considered. It is shown that, in the absence of basis reconciliation, a protocol with the tetrahedral alphabet has the highest critical error rate among the protocols considered, while after the basis reconciliation, a protocol with the continual alphabet possesses the highest critical error rate. (quantum optics and quantum computation)
Quantum cryptography and applications in the optical fiber network
NASA Astrophysics Data System (ADS)
Luo, Yuhui
2005-09-01
Quantum cryptography, as part of quantum information and communications, can provide absolute security for information transmission because it is established on the fundamental laws of quantum theory, such as the principle of uncertainty, No-cloning theorem and quantum entanglement. In this thesis research, a novel scheme to implement quantum key distribution based on multiphoton entanglement with a new protocol is proposed. Its advantages are: a larger information capacity can be obtained with a longer transmission distance and the detection of multiple photons is easier than that of a single photon. The security and attacks pertaining to such a system are also studied. Next, a quantum key distribution over wavelength division multiplexed (WDM) optical fiber networks is realized. Quantum key distribution in networks is a long-standing problem for practical applications. Here we combine quantum cryptography and WDM to solve this problem because WDM technology is universally deployed in the current and next generation fiber networks. The ultimate target is to deploy quantum key distribution over commercial networks. The problems arising from the networks are also studied in this part. Then quantum key distribution in multi-access networks using wavelength routing technology is investigated in this research. For the first time, quantum cryptography for multiple individually targeted users has been successfully implemented in sharp contrast to that using the indiscriminating broadcasting structure. It overcomes the shortcoming that every user in the network can acquire the quantum key signals intended to be exchanged between only two users. Furthermore, a more efficient scheme of quantum key distribution is adopted, hence resulting in a higher key rate. Lastly, a quantum random number generator based on quantum optics has been experimentally demonstrated. This device is a key component for quantum key distribution as it can create truly random numbers, which is an
Quantum cryptography on multi-user network architectures
NASA Astrophysics Data System (ADS)
Kumavor, Patrick D.; Beal, Alan C.; Yelin, Susanne; Donkor, Eric; Wang, Bing C.
2006-05-01
Quantum cryptography applies the uncertainty principle and the no-cloning theorem to allow to parties to share a secret key over an ultra-secure link. Present quantum cryptography technologies provide encryption key distribution only between two users. However, practical implementations of encryption key distribution schemes require establishing secure quantum communications amongst multiple users. This paper looks at some of the advantages and drawbacks of some common network topologies that could be used in sending cryptographic keys across a network consisting of multiple users. These topologies are the star, ring, and bus networks. Their performances are compared and analyzed using quantum bit error rate analysis. The paper also presents an experimental demonstration of a six-user quantum key distribution network implemented on a bus topology.
NASA Astrophysics Data System (ADS)
Lütkenhaus, N.; Shields, A. J.
2009-04-01
Quantum cryptography, and especially quantum key distribution (QKD), is steadily progressing to become a viable tool for cryptographic services. In recent years we have witnessed a dramatic increase in the secure bit rate of QKD, as well as its extension to ever longer fibre- and air-based links and the emergence of metro-scale trusted networks. In the foreseeable future even global-scale communications may be possible using quantum repeaters or Earth-satellite links. A handful of start-ups and some bigger companies are already active in the field. The launch of an initiative to form industrial standards for QKD, under the auspices of the European Telecommunication Standards Institute, described in the paper by Laenger and Lenhart in this Focus Issue, can be taken as a sign of the growing commercial interest. Recent progress has seen an increase in the secure bit rate of QKD links, by orders of magnitude, to over 1 Mb s-1. This has resulted mainly from an improvement in the detection technology. Here changes in the way conventional semiconductor detectors are gated, as well as the development of novel devices based on non-linear processes and superconducting materials, are leading the way. Additional challenges for QKD at GHz clock rates include the design of high speed electronics, remote synchronization and high rate random number generation. Substantial effort is being devoted to increasing the range of individual links, which is limited by attenuation and other losses in optical fibres and air links. An important advance in the past few years has been the introduction of protocols with the same scaling as an ideal single-photon set-up. The good news is that these schemes use standard optical devices, such as weak laser pulses. Thanks to these new protocols and improvements in the detection technology, the range of a single fibre link can exceed a few hundred km. Outstanding issues include proving the unconditional security of some of the schemes. Much of the
Quantum Cryptography Over 24 km of Underground Optical Fibers
NASA Astrophysics Data System (ADS)
Hughes, Richard; Luther, Gabriel; Morgan, George; Peterson, Charles; Simmons, Charles
1997-04-01
The secure distribution of the secret random bit sequences known as ''key'' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We are performing quantum cryptography over 24-km of underground optical fiber using non-orthogonal single-photon interference states. Key material is built up by transmitting a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. Our experiment demonstrates that secure, real-time key generation over "open" multi-km node-to-node optical fiber communications links is feasible.
Coherent eavesdropping strategies for the four state quantum cryptography protocol
NASA Astrophysics Data System (ADS)
Cirac, J. I.; Gisin, N.
1997-02-01
An elementary derivation of best eavesdropping strategies for the four state BB84 quantum cryptography protocol is presented, for both incoherent and two-qubit coherent attacks. While coherent attacks do not help Eve to obtain more information, they are more powerful to reveal the whole message sent by Alice. Our results are based on symmetric eavesdropping strategies, which we show to be sufficient to analyze these kind of problems.
Practical Quantum Cryptography for Secure Free-Space Communications
Buttler, W.T.; Hughes, R.J.; Kwiat, P.G.; Lamoreaux, S.K.; Morgan, G.L.; Nordholt, J.E.; Peterson, C.G.
1999-02-01
Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.
Quantum Overloading Cryptography Using Single-Photon Nonlocality
NASA Astrophysics Data System (ADS)
Tan, Yong-Gang; Cai, Qing-Yu; Shi, Ting-Yun
2007-08-01
Using the single-photon nonlocality, we propose a quantum novel overloading cryptography scheme, in which a single photon carries two bits information in one-way quantum channel. Two commutative modes of the single photon, the polarization mode and the spatial mode, are used to encode secret information. Strict time windows are set to detect the impersonation attack. The spatial mode which denotes the existence of photons is noncommutative with the phase of the photon, so that our scheme is secure against photon-number-splitting attack. Our protocol may be secure against individual attack.
An Online Banking System Based on Quantum Cryptography Communication
NASA Astrophysics Data System (ADS)
Zhou, Ri-gui; Li, Wei; Huan, Tian-tian; Shen, Chen-yi; Li, Hai-sheng
2014-07-01
In this paper, an online banking system has been built. Based on quantum cryptography communication, this system is proved unconditional secure. Two sets of GHZ states are applied, which can ensure the safety of purchase and payment, respectively. In another word, three trading participants in each triplet state group form an interdependent and interactive relationship. In the meantime, trading authorization and blind signature is introduced by means of controllable quantum teleportation. Thus, an effective monitor is practiced on the premise that the privacy of trading partners is guaranteed. If there is a dispute or deceptive behavior, the system will find out the deceiver immediately according to the relationship mentioned above.
NASA Astrophysics Data System (ADS)
Sych, D. V.; Grishanin, Boris A.; Zadkov, Viktor N.
2005-01-01
The problem of increasing the critical error rate of quantum-cryptography protocols by varying a set of letters in a quantum alphabet for space of a fixed dimensionality is studied. Quantum alphabets forming regular polyhedra on the Bloch sphere and the continual alphabet equally including all the quantum states are considered. It is shown that, in the absence of basis reconciliation, a protocol with the tetrahedral alphabet has the highest critical error rate among the protocols considered, while after the basis reconciliation, a protocol with the continual alphabet possesses the highest critical error rate.
Infeasibility of Quantum Cryptography Without Eavesdropping Check
NASA Astrophysics Data System (ADS)
Yang, Wei; Huang, Liusheng; Song, Fang; Wang, Qiyan
Secure key distribution is impossible in pure classical environment. Unconditional secure key distribution is available when quantum means are introduced, assisted by a classical communication channel. What is possible when a quantum key distribution scheme is without classical communication? We present a general model with this constraint and show that quantum key distribution without classical eavesdropping check is in principle impossible. For an adversary can always succeed in obtaining the secret key via a special case of man-in-the-middle attack, namely intercept-and-forward attack without any risk of being captured.
Some conservative estimates in quantum cryptography
Molotkov, S. N.
2006-08-15
Relationship is established between the security of the BB84 quantum key distribution protocol and the forward and converse coding theorems for quantum communication channels. The upper bound Q{sub c} {approx} 11% on the bit error rate compatible with secure key distribution is determined by solving the transcendental equation H(Q{sub c})=C-bar({rho})/2, where {rho} is the density matrix of the input ensemble, C-bar({rho}) is the classical capacity of a noiseless quantum channel, and H(Q) is the capacity of a classical binary symmetric channel with error rate Q.
Quantum random number generators and their applications in cryptography
NASA Astrophysics Data System (ADS)
Stipcevic, Mario
2012-06-01
Random number generators (RNG) are an important resource in many areas: cryptography (both quantum and classical), probabilistic computation (Monte Carlo methods), numerical simulations, industrial testing and labeling, hazard games, scientific research etc. Because today's computers are deterministic, they can not create random numbers unless complemented with a physical RNG. Randomness of a RNG can be defined and scientifically characterized and measured. Especially valuable is the information-theoretic provable RNG which, at state of the art, seem to be possible only by harvest of randomness inherent to certain (simple) quantum systems and such a generator we call Quantum RNG (QRNG). On the other hand, current industry standards dictate use of RNGs based on free running oscillators (FRO) whose randomness is derived from electronics noise present in logic circuits and which, although quantum in nature, cannot be strictly proven. This approach is currently used in FPGA and ASIC chips. We compare weak and strong aspects of the two approaches for use in cryptography and in general. We also give an alternative definition of randomness, discuss usage of single photon detectors in realization of QRNGs and give several examples where QRNG can significantly improve security of a cryptographic system.
High-rate measurement-device-independent quantum cryptography
NASA Astrophysics Data System (ADS)
Pirandola, Stefano; Ottaviani, Carlo; Spedalieri, Gaetana; Weedbrook, Christian; Braunstein, Samuel L.; Lloyd, Seth; Gehring, Tobias; Jacobsen, Christian S.; Andersen, Ulrik L.
2015-06-01
Quantum cryptography achieves a formidable task—the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate quantum networks where devices securely connect to nearby access points or proxy servers.
Quantum cryptography for secure free-space communications
NASA Astrophysics Data System (ADS)
Hughes, Richard J.; Buttler, William T.; Kwiat, Paul G.; Lamoreaux, Steve K.; Luther, Gabriel G.; Morgan, George L.; Nordholt, Jane E.; Peterson, C. Glen
1999-04-01
The secure distribution of the secret random bit sequences known as 'key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non- orthogonal photon polarization states to generate shared key material over line-of-sight optical links. Key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. We have developed and tested a free-space quantum key distribution (QKD) system over an outdoor optical path of approximately 1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite QKD.
Quantum cryptography for secure free-space communications
Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.; Lamoreaux, S.K.; Luther, G.G.; Morgan, G.L.; Nordholt, J.E.; Peterson, C.G.
1999-03-01
The secure distribution of the secret random bit sequences known as key material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg`s uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). The authors have developed experimental quantum cryptography systems based on the transmission of non-orthogonal photon polarization states to generate shared key material over line-of-sight optical links. Key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. The authors have developed and tested a free-space quantum key distribution (QKD) system over an outdoor optical path of {approximately}1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, they examine the feasibility of surface to satellite QKD.
Quantum cryptography: Round-robin with photons
NASA Astrophysics Data System (ADS)
Fröhlich, Bernd; Yuan, Zhiliang
2015-12-01
Last year the common notion that signal disturbance has to be monitored in a quantum cryptographic link to guarantee secrecy was challenged by a new protocol. The formidable task of demonstrating it experimentally has now been achieved.
Practical implementation of multilevel quantum cryptography
Kulik, S. P. Maslennikov, G. A.; Moreva, E. V.
2006-05-15
The physical principles of a quantum key distribution protocol using four-level optical systems are discussed. Quantum information is encoded into polarization states created by frequency-nondegenerate spontaneous parametric down-conversion in collinear geometry. In the scheme under analysis, the required nonorthogonal states are generated in a single nonlinear crystal. All states in the selected basis are measured deterministically. The results of initial experiments on transformation of the basis polarization states of a four-level optical system are discussed.
Deterministic and efficient quantum cryptography based on Bell's theorem
Chen Zengbing; Pan Jianwei; Zhang Qiang; Bao Xiaohui; Schmiedmayer, Joerg
2006-05-15
We propose a double-entanglement-based quantum cryptography protocol that is both efficient and deterministic. The proposal uses photon pairs with entanglement both in polarization and in time degrees of freedom; each measurement in which both of the two communicating parties register a photon can establish one and only one perfect correlation, and thus deterministically create a key bit. Eavesdropping can be detected by violation of local realism. A variation of the protocol shows a higher security, similar to the six-state protocol, under individual attacks. Our scheme allows a robust implementation under the current technology.
Device-independent quantum cryptography for continuous variables
NASA Astrophysics Data System (ADS)
Marshall, Kevin; Weedbrook, Christian
2014-10-01
We present a device-independent quantum cryptography protocol for continuous variables. Our scheme is based on the Gottesman-Kitaev-Preskill encoding scheme whereby a qubit is embedded in the infinite-dimensional space of a quantum harmonic oscillator. The application of discrete-variable device-independent quantum key distribution to this encoding enables a continuous-variable analog. Since the security of this protocol is based on discrete variables we inherit by default security against collective attacks and, under certain memoryless assumptions, coherent attacks. We find that our protocol is valid over the same distances as its discrete-variable counterpart, except that we are able to take advantage of high efficiency commercially available detectors where, for the most part, only homodyne detection is required. This offers the prospect of closing the loopholes associated with Bell inequalities.
NASA Astrophysics Data System (ADS)
Lütkenhaus, N.; Shields, A. J.
2009-04-01
Quantum cryptography, and especially quantum key distribution (QKD), is steadily progressing to become a viable tool for cryptographic services. In recent years we have witnessed a dramatic increase in the secure bit rate of QKD, as well as its extension to ever longer fibre- and air-based links and the emergence of metro-scale trusted networks. In the foreseeable future even global-scale communications may be possible using quantum repeaters or Earth-satellite links. A handful of start-ups and some bigger companies are already active in the field. The launch of an initiative to form industrial standards for QKD, under the auspices of the European Telecommunication Standards Institute, described in the paper by Laenger and Lenhart in this Focus Issue, can be taken as a sign of the growing commercial interest. Recent progress has seen an increase in the secure bit rate of QKD links, by orders of magnitude, to over 1 Mb s-1. This has resulted mainly from an improvement in the detection technology. Here changes in the way conventional semiconductor detectors are gated, as well as the development of novel devices based on non-linear processes and superconducting materials, are leading the way. Additional challenges for QKD at GHz clock rates include the design of high speed electronics, remote synchronization and high rate random number generation. Substantial effort is being devoted to increasing the range of individual links, which is limited by attenuation and other losses in optical fibres and air links. An important advance in the past few years has been the introduction of protocols with the same scaling as an ideal single-photon set-up. The good news is that these schemes use standard optical devices, such as weak laser pulses. Thanks to these new protocols and improvements in the detection technology, the range of a single fibre link can exceed a few hundred km. Outstanding issues include proving the unconditional security of some of the schemes. Much of the
Measurement-device-independent quantum cryptography
Xu, Feihu; Curty, Marcos; Qi, Bing; Lo, Hoi-Kwong
2014-12-18
In theory, quantum key distribution (QKD) provides information-theoretic security based on the laws of physics. Owing to the imperfections of real-life implementations, however, there is a big gap between the theory and practice of QKD, which has been recently exploited by several quantum hacking activities. To fill this gap, a novel approach, called measurement-device-independent QKD (mdiQKD), has been proposed. In addition, it can remove all side-channels from the measurement unit, arguably the most vulnerable part in QKD systems, thus offering a clear avenue toward secure QKD realisations. In this study, we review the latest developments in the framework of mdiQKD,more » together with its assumptions, strengths, and weaknesses.« less
Measurement-device-independent quantum cryptography
Xu, Feihu; Curty, Marcos; Qi, Bing; Lo, Hoi-Kwong
2014-12-18
In theory, quantum key distribution (QKD) provides information-theoretic security based on the laws of physics. Owing to the imperfections of real-life implementations, however, there is a big gap between the theory and practice of QKD, which has been recently exploited by several quantum hacking activities. To fill this gap, a novel approach, called measurement-device-independent QKD (mdiQKD), has been proposed. In addition, it can remove all side-channels from the measurement unit, arguably the most vulnerable part in QKD systems, thus offering a clear avenue toward secure QKD realisations. In this study, we review the latest developments in the framework of mdiQKD, together with its assumptions, strengths, and weaknesses.
Superlinear threshold detectors in quantum cryptography
Lydersen, Lars; Maroey, Oystein; Skaar, Johannes; Makarov, Vadim; Jain, Nitin; Wittmann, Christoffer; Marquardt, Christoph; Leuchs, Gerd
2011-09-15
We introduce the concept of a superlinear threshold detector, a detector that has a higher probability to detect multiple photons if it receives them simultaneously rather than at separate times. Highly superlinear threshold detectors in quantum key distribution systems allow eavesdropping the full secret key without being revealed. Here, we generalize the detector control attack, and analyze how it performs against quantum key distribution systems with moderately superlinear detectors. We quantify the superlinearity in superconducting single-photon detectors based on earlier published data, and gated avalanche photodiode detectors based on our own measurements. The analysis shows that quantum key distribution systems using detector(s) of either type can be vulnerable to eavesdropping. The avalanche photodiode detector becomes superlinear toward the end of the gate. For systems expecting substantial loss, or for systems not monitoring loss, this would allow eavesdropping using trigger pulses containing less than 120 photons per pulse. Such an attack would be virtually impossible to catch with an optical power meter at the receiver entrance.
Free-space quantum cryptography with quantum and telecom communication channels
NASA Astrophysics Data System (ADS)
Toyoshima, Morio; Takayama, Yoshihisa; Klaus, Werner; Kunimori, Hiroo; Fujiwara, Mikio; Sasaki, Masahide
2008-07-01
Quantum cryptography is a new technique that uses the laws of physics to transmit information securely. In such systems, the vehicle to transfer quantum information is a single photon. However, the transmission distance is limited by the absorption of photons in an optical fiber in which the maximum demonstrated range is about 100 km. Free-space quantum cryptography between a ground station and a satellite is a way of sending the quantum information further distances than that with optical fibers since there is no birefringence effect in the atmosphere. At the National Institute of Information and Communications Technology (NICT), the laser communication demonstration between the NICT optical ground station and a low earth orbit satellite was successfully conducted in 2006. For such space communication links, free-space quantum cryptography is considered to be an important application in the future. We have developed a prototype system for free-space quantum cryptography using a weak coherent light and a telecom communication channel. The preliminary results are presented.
Practical free-space quantum cryptography
Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.; Lamoreaux, S.K.; Luther, G.G.; Morgan, G.L.; Nordholt, J.E.; Peterson, C.G.; Simmons, C.M.
1998-12-01
An experimental free-space quantum key distribution (QKD) system has been tested over an outdoor optical path of {approx} 1 km under nighttime conditions at Los Alamos National Laboratory. This system employs the Bennett 92 protocol; here the authors give a brief overview of this protocol, and describe the experimental implementation of it. An analysis of the system efficiency is presented, as well as a description of the error detection protocol, which employs a two-dimensional parity check scheme. Finally, the susceptibility of this system to eavesdropping by various techniques is determined, and the effectiveness of privacy amplification procedures is discussed. The conclusions are that free-space QKD is both effective and secure; possible applications include the rekeying of satellites in low earth orbit.
Tight finite-key analysis for quantum cryptography
NASA Astrophysics Data System (ADS)
Tomamichel, Marco; Lim, Charles Ci Wen; Gisin, Nicolas; Renner, Renato
2012-01-01
Despite enormous theoretical and experimental progress in quantum cryptography, the security of most current implementations of quantum key distribution is still not rigorously established. One significant problem is that the security of the final key strongly depends on the number, M, of signals exchanged between the legitimate parties. Yet, existing security proofs are often only valid asymptotically, for unrealistically large values of M. Another challenge is that most security proofs are very sensitive to small differences between the physical devices used by the protocol and the theoretical model used to describe them. Here we show that these gaps between theory and experiment can be simultaneously overcome by using a recently developed proof technique based on the uncertainty relation for smooth entropies.
Tight finite-key analysis for quantum cryptography.
Tomamichel, Marco; Lim, Charles Ci Wen; Gisin, Nicolas; Renner, Renato
2012-01-01
Despite enormous theoretical and experimental progress in quantum cryptography, the security of most current implementations of quantum key distribution is still not rigorously established. One significant problem is that the security of the final key strongly depends on the number, M, of signals exchanged between the legitimate parties. Yet, existing security proofs are often only valid asymptotically, for unrealistically large values of M. Another challenge is that most security proofs are very sensitive to small differences between the physical devices used by the protocol and the theoretical model used to describe them. Here we show that these gaps between theory and experiment can be simultaneously overcome by using a recently developed proof technique based on the uncertainty relation for smooth entropies. PMID:22252558
Experimental quantum cryptography scheme based on orthogonal states: preliminary results
NASA Astrophysics Data System (ADS)
Avella, Alessio; Brida, Giorgio; Degiovanni, Ivo P.; Genovese, Marco; Gramegna, Marco; Traina, Paolo
2010-04-01
Since, in general, non-orthogonal states cannot be cloned, any eavesdropping attempt in a Quantum Communication scheme using non-orthogonal states as carriers of information introduces some errors in the transmission, leading to the possibility of detecting the spy. Usually, orthogonal states are not used in Quantum Cryptography schemes since they can be faithfully cloned without altering the transmitted data. Nevertheless, L. Goldberg and L. Vaidman [Phys. Rev. Lett. 75 (7), pp. 12391243, 1995] proposed a protocol in which, even if the data exchange is realized using two orthogonal states, any attempt to eavesdrop is detectable by the legal users. In this scheme the orthogonal states are superpositions of two localized wave packets which travel along separate channels, i.e. two different paths inside a balanced Mach-Zehnder interferometer. Here we present an experiment realizing this scheme.
Experimental quantum-cryptography scheme based on orthogonal states
NASA Astrophysics Data System (ADS)
Avella, Alessio; Brida, Giorgio; Degiovanni, Ivo Pietro; Genovese, Marco; Gramegna, Marco; Traina, Paolo
2010-12-01
Since, in general, nonorthogonal states cannot be cloned, any eavesdropping attempt in a quantum-communication scheme using nonorthogonal states as carriers of information introduces some errors in the transmission, leading to the possibility of detecting the spy. Usually, orthogonal states are not used in quantum-cryptography schemes since they can be faithfully cloned without altering the transmitted data. Nevertheless, L. Goldberg and L. Vaidman [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.75.1239 75, 1239 (1995)] proposed a protocol in which, even if the data exchange is realized using two orthogonal states, any attempt to eavesdrop is detectable by the legal users. In this scheme the orthogonal states are superpositions of two localized wave packets traveling along separate channels. Here we present an experiment realizing this scheme.
Experimental quantum-cryptography scheme based on orthogonal states
Avella, Alessio; Brida, Giorgio; Degiovanni, Ivo Pietro; Genovese, Marco; Gramegna, Marco; Traina, Paolo
2010-12-15
Since, in general, nonorthogonal states cannot be cloned, any eavesdropping attempt in a quantum-communication scheme using nonorthogonal states as carriers of information introduces some errors in the transmission, leading to the possibility of detecting the spy. Usually, orthogonal states are not used in quantum-cryptography schemes since they can be faithfully cloned without altering the transmitted data. Nevertheless, L. Goldberg and L. Vaidman [Phys. Rev. Lett. 75, 1239 (1995)] proposed a protocol in which, even if the data exchange is realized using two orthogonal states, any attempt to eavesdrop is detectable by the legal users. In this scheme the orthogonal states are superpositions of two localized wave packets traveling along separate channels. Here we present an experiment realizing this scheme.
Quantum cryptography in real-life applications: Assumptions and security
NASA Astrophysics Data System (ADS)
Zhao, Yi
Quantum cryptography, or quantum key distribution (QKD), provides a means of unconditionally secure communication. The security is in principle based on the fundamental laws of physics. Security proofs show that if quantum cryptography is appropriately implemented, even the most powerful eavesdropper cannot decrypt the message from a cipher. The implementations of quantum crypto-systems in real life may not fully comply with the assumptions made in the security proofs. Such discrepancy between the experiment and the theory can be fatal to the security of a QKD system. In this thesis we address a number of these discrepancies. A perfect single-photon source is often assumed in many security proofs. However, a weak coherent source is widely used in a real-life QKD implementation. Decoy state protocols have been proposed as a novel approach to dramatically improve the performance of a weak coherent source based QKD implementation without jeopardizing its security. Here, we present the first experimental demonstrations of decoy state protocols. Our experimental scheme was later adopted by most decoy state QKD implementations. In the security proof of decoy state protocols as well as many other QKD protocols, it is widely assumed that a sender generates a phase-randomized coherent state. This assumption has been enforced in few implementations. We close this gap in two steps: First, we implement and verify the phase randomization experimentally; second, we prove the security of a QKD implementation without the coherent state assumption. In many security proofs of QKD, it is assumed that all the detectors on the receiver's side have identical detection efficiencies. We show experimentally that this assumption may be violated in a commercial QKD implementation due to an eavesdropper's malicious manipulation. Moreover, we show that the eavesdropper can learn part of the final key shared by the legitimate users as a consequence of this violation of the assumptions.
Effect of source tampering in the security of quantum cryptography
NASA Astrophysics Data System (ADS)
Sun, Shi-Hai; Xu, Feihu; Jiang, Mu-Sheng; Ma, Xiang-Chun; Lo, Hoi-Kwong; Liang, Lin-Mei
2015-08-01
The security of source has become an increasingly important issue in quantum cryptography. Based on the framework of measurement-device-independent quantum key distribution (MDI-QKD), the source becomes the only region exploitable by a potential eavesdropper (Eve). Phase randomization is a cornerstone assumption in most discrete-variable (DV) quantum communication protocols (e.g., QKD, quantum coin tossing, weak-coherent-state blind quantum computing, and so on), and the violation of such an assumption is thus fatal to the security of those protocols. In this paper, we show a simple quantum hacking strategy, with commercial and homemade pulsed lasers, by Eve that allows her to actively tamper with the source and violate such an assumption, without leaving a trace afterwards. Furthermore, our attack may also be valid for continuous-variable (CV) QKD, which is another main class of QKD protocol, since, excepting the phase random assumption, other parameters (e.g., intensity) could also be changed, which directly determine the security of CV-QKD.
Quantum cryptography and authentication with low key-consumption
NASA Astrophysics Data System (ADS)
Abidin, A.; Pacher, C.; Lorünser, T.; Larsson, J.-Å.; Peev, M.
2011-11-01
Quantum Key Distribution (QKD - also referred to as Quantum Cryptography) is a technique for secret key agreement. It has been shown that QKD rigged with Information-Theoretic Secure (ITS) authentication (using secret key) of the classical messages transmitted during the key distribution protocol is also ITS. Note, QKD without any authentication can trivially be broken by man-in-the-middle attacks. Here, we study an authentication method that was originally proposed because of its low key consumption; a two-step authentication that uses a publicly known hash function, followed by a secret strongly universal2 hash function, which is exchanged each round. This two-step authentication is not information-theoretically secure but it was argued that nevertheless it does not compromise the security of QKD. In the current contribution we study intrinsic weaknesses of this approach under the common assumption that the QKD adversary has access to unlimited resources including quantum memories. We consider one implementation of Quantum Cryptographic protocols that use such authentication and demonstrate an attack that fully extract the secret key. Even including the final key from the protocol in the authentication does not rule out the possibility of these attacks. To rectify the situation, we propose a countermeasure that, while not information-theoretically secure, restores the need for very large computing power for the attack to work. Finally, we specify conditions that must be satisfied by the two-step authentication in order to restore information-theoretic security.
The (in)adequacy of applicative use of quantum cryptography in wireless sensor networks
NASA Astrophysics Data System (ADS)
Turkanović, Muhamed; Hölbl, Marko
2014-10-01
Recently quantum computation and cryptography principles are exploited in the design of security systems for wireless sensor networks (WSNs), which are consequently named as quantum WSN. Quantum cryptography is presumably secure against any eavesdropper and thus labeled as providing unconditional security. This paper tries to analyze the aspect of the applicative use of quantum principles in WSN. The outcome of the analysis elaborates a summary about the inadequacy of applicative use of quantum cryptography in WSN and presents an overview of all possible applicative challenges and problems while designing quantum-based security systems for WSN. Since WSNs are highly complex frameworks, with many restrictions and constraints, every security system has to be fully compatible and worthwhile. The aim of the paper was to contribute a verdict about this topic, backed up by equitable facts.
Free-Space Quantum Cryptography in a Hydrogen Fraunhofer Window
NASA Astrophysics Data System (ADS)
Rogers, Daniel; Bienfang, Joshua; Mink, Alan; Hershman, Barry; Nakassis, Anastase; Tang, Xiao; Ma, Lijun; Su, David; Williams, Carl; Clark, Charles
2006-05-01
Quantum key distribution (QKD) has shown the potential for the production of cryptographic key for ultra-secure communications. The performance of any QKD system is ultimately limited by the signal to noise ratio on the single-photon channel, and over most useful communications links the resulting in key rates are impractical for performing continuous one-time-pad encryption of today's broadband communications. We have adapted clock and data recovery techniques from modern telecommunications practice to increase the repetition rate of a free-space QKD system by roughly 2 orders of magnitude over previous demonstrations. We have also designed the system to operate in the H-α Fraunhofer window at 656.28 nm, where the solar background is reduced by roughly 7 dB. To achieve high repetition rates this system takes advantage of silicon single-photon avalanche photodiodes with < 50 ps timing resolution and high detection efficiency in the visible region. This free-space QKD system is designed to operate at a repetition rate of 2.5 GHz. We have identified scalable solutions for delivering sustained one-time-pad encryption at 10 Mbps, thus making it possible to integrate quantum cryptography with first-generation Ethernet protocols.
Quantum cryptography using coherent states: Randomized encryption and key generation
NASA Astrophysics Data System (ADS)
Corndorf, Eric
With the advent of the global optical-telecommunications infrastructure, an increasing number of individuals, companies, and agencies communicate information with one another over public networks or physically-insecure private networks. While the majority of the traffic flowing through these networks requires little or no assurance of secrecy, the same cannot be said for certain communications between banks, between government agencies, within the military, and between corporations. In these arenas, the need to specify some level of secrecy in communications is a high priority. While the current approaches to securing sensitive information (namely the public-key-cryptography infrastructure and deterministic private-key ciphers like AES and 3DES) seem to be cryptographically strong based on empirical evidence, there exist no mathematical proofs of secrecy for any widely deployed cryptosystem. As an example, the ubiquitous public-key cryptosystems infer all of their secrecy from the assumption that factoring of the product of two large primes is necessarily time consuming---something which has not, and perhaps cannot, be proven. Since the 1980s, the possibility of using quantum-mechanical features of light as a physical mechanism for satisfying particular cryptographic objectives has been explored. This research has been fueled by the hopes that cryptosystems based on quantum systems may provide provable levels of secrecy which are at least as valid as quantum mechanics itself. Unfortunately, the most widely considered quantum-cryptographic protocols (BB84 and the Ekert protocol) have serious implementation problems. Specifically, they require quantum-mechanical states which are not readily available, and they rely on unproven relations between intrusion-level detection and the information available to an attacker. As a result, the secrecy level provided by these experimental implementations is entirely unspecified. In an effort to provably satisfy the cryptographic
Topics in quantum cryptography, quantum error correction, and channel simulation
NASA Astrophysics Data System (ADS)
Luo, Zhicheng
In this thesis, we mainly investigate four different topics: efficiently implementable codes for quantum key expansion [51], quantum error-correcting codes based on privacy amplification [48], private classical capacity of quantum channels [44], and classical channel simulation with quantum side information [49, 50]. For the first topic, we propose an efficiently implementable quantum key expansion protocol, capable of increasing the size of a pre-shared secret key by a constant factor. Previously, the Shor-Preskill proof [64] of the security of the Bennett-Brassard 1984 (BB84) [6] quantum key distribution protocol relied on the theoretical existence of good classical error-correcting codes with the "dual-containing" property. But the explicit and efficiently decodable construction of such codes is unknown. We show that we can lift the dual-containing constraint by employing the non-dual-containing codes with excellent performance and efficient decoding algorithms. For the second topic, we propose a construction of Calderbank-Shor-Steane (CSS) [19, 68] quantum error-correcting codes, which are originally based on pairs of mutually dual-containing classical codes, by combining a classical code with a two-universal hash function. We show, using the results of Renner and Koenig [57], that the communication rates of such codes approach the hashing bound on tensor powers of Pauli channels in the limit of large block-length. For the third topic, we prove a regularized formula for the secret key assisted capacity region of a quantum channel for transmitting private classical information. This result parallels the work of Devetak on entanglement assisted quantum communication capacity. This formula provides a new family protocol, the private father protocol, under the resource inequality framework that includes the private classical communication without the assisted secret keys as a child protocol. For the fourth topic, we study and solve the problem of classical channel
NASA Astrophysics Data System (ADS)
Zhang, Sheng; Wang, Jian; Tang, Chao-Jing
2012-06-01
Counterfactual quantum cryptography, recently proposed by Noh, is featured with no transmission of signal particles. This exhibits evident security advantages, such as its immunity to the well-known photon-number-splitting attack. In this paper, the theoretical security of counterfactual quantum cryptography protocol against the general intercept-resend attacks is proved by bounding the information of an eavesdropper Eve more tightly than in Yin's proposal [Phys. Rev. A 82 042335 (2010)]. It is also shown that practical counterfactual quantum cryptography implementations may be vulnerable when equipped with imperfect apparatuses, by proving that a negative key rate can be achieved when Eve launches a time-shift attack based on imperfect detector efficiency.
A Secure Key Distribution System of Quantum Cryptography Based on the Coherent State
NASA Technical Reports Server (NTRS)
Guo, Guang-Can; Zhang, Xiao-Yu
1996-01-01
The cryptographic communication has a lot of important applications, particularly in the magnificent prospects of private communication. As one knows, the security of cryptographic channel depends crucially on the secrecy of the key. The Vernam cipher is the only cipher system which has guaranteed security. In that system the key must be as long as the message and most be used only once. Quantum cryptography is a method whereby key secrecy can be guaranteed by a physical law. So it is impossible, even in principle, to eavesdrop on such channels. Quantum cryptography has been developed in recent years. Up to now, many schemes of quantum cryptography have been proposed. Now one of the main problems in this field is how to increase transmission distance. In order to use quantum nature of light, up to now proposed schemes all use very dim light pulses. The average photon number is about 0.1. Because of the loss of the optical fiber, it is difficult for the quantum cryptography based on one photon level or on dim light to realize quantum key-distribution over long distance. A quantum key distribution based on coherent state is introduced in this paper. Here we discuss the feasibility and security of this scheme.
Security improvement by using a modified coherent state for quantum cryptography
Lu, Y.J.; Zhu, Luobei; Ou, Z.Y.
2005-03-01
Weak coherent states as a photon source for quantum cryptography have a limit in secure data rate and transmission distance because of the presence of multiphoton events and loss in transmission line. Two-photon events in a coherent state can be taken out by a two-photon interference scheme. We investigate the security issue of utilizing this modified coherent state in quantum cryptography. A 4-dB improvement in the secure data rate or a nearly twofold increase in transmission distance over the coherent state are found. With a recently proposed and improved encoding strategy, further improvement is possible.
Quantum Cryptography for Secure Communications to Low-Earth Orbit Satellites
Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.; Lamoreaux, S.K.; Morgan, G.L.; Peterson, C.G.; Twyeffort, E.; Simmons, C.M.; Nordholt, J.E.
1999-06-03
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics. An adversary can neither successfully tap the quantum transmissions, nor evade detection. Key material is built up using the transmission of a single-photon per bit. We have developed an experimental quantum cryptography system based on the transmission of non-orthogonal single-photon polarization states to generate shared key material over line-of-sight optical links. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on in orbit.
Quantum-tomographic cryptography with a semiconductor single-photon source
Kaszlikowski, D.; Yang, L.J.; Yong, L.S.; Willeboordse, F.H.; Kwek, L.C.
2005-09-15
We analyze the security of so-called quantum-tomographic cryptography with the source producing entangled photons via an experimental scheme proposed by Fattal et al. [Phys. Rev. Lett. 92, 37903 (2004)]. We determine the range of the experimental parameters for which the protocol is secure against the most general incoherent attacks.
On a two-pass scheme without a faraday mirror for free-space relativistic quantum cryptography
Kravtsov, K. S.; Radchenko, I. V.; Korol'kov, A. V.; Kulik, S. P.; Molotkov, S. N.
2013-05-15
The stability of destructive interference independent of the input polarization and the state of a quantum communication channel in fiber optic systems used in quantum cryptography plays a principal role in providing the security of communicated keys. A novel optical scheme is proposed that can be used both in relativistic quantum cryptography for communicating keys in open space and for communicating them over fiber optic lines. The scheme ensures stability of destructive interference and admits simple automatic balancing of a fiber interferometer.
Conceptual designs of onboard transceivers for ground-to-satellite quantum cryptography
NASA Astrophysics Data System (ADS)
Toyoshima, Morio; Shoji, Yozo; Takayama, Yoshihisa; Kunimori, Hiroo; Takeoka, Masahiro; Fujiwara, Mikio; Sasaki, Masahide
2009-05-01
A free-space quantum key distribution system is being developed by the National Institute of Information and Communications Technology (NICT) in Koganei, Japan. Quantum cryptography is a new technique for transmitting information where the security is guaranteed by the laws of physics. In such systems, a single photon is used for the quantum information. However, since the transmission distance in optical fibers is limited by the absorption of photons by the fiber, the maximum demonstrated range has been limited to about 100 km. Free-space quantum cryptography between an optical ground station and a satellite is a possible solution to extend the distance for a quantum network beyond the limits of optical fibers. At NICT, a laser communication demonstration between the NICT optical ground station and a low earth orbit satellite was successfully conducted in 2006. The use of free-space quantum key distribution for such space communication links is considered an important future application. This paper presents conceptual designs for the onboard transceivers for satellite quantum cryptography
Comment on 'Two-way protocols for quantum cryptography with a nonmaximally entangled qubit pair'
Qin Sujuan; Gao Fei; Wen Qiaoyan; Guo Fenzhuo
2010-09-15
Three protocols of quantum cryptography with a nonmaximally entangled qubit pair [Phys. Rev. A 80, 022323 (2009)] were recently proposed by Shimizu, Tamaki, and Fukasaka. The security of these protocols is based on the quantum-mechanical constraint for a state transformation between nonmaximally entangled states. However, we find that the second protocol is vulnerable under the correlation-elicitation attack. An eavesdropper can obtain the encoded bit M although she has no knowledge about the random bit R.
The Structure of Bipartite Quantum States - Insights from Group Theory and Cryptography
NASA Astrophysics Data System (ADS)
Christandl, Matthias
2006-04-01
This thesis presents a study of the structure of bipartite quantum states. In the first part, the representation theory of the unitary and symmetric groups is used to analyse the spectra of quantum states. In particular, it is shown how to derive a one-to-one relation between the spectra of a bipartite quantum state and its reduced states, and the Kronecker coefficients of the symmetric group. In the second part, the focus lies on the entanglement of bipartite quantum states. Drawing on an analogy between entanglement distillation and secret-key agreement in classical cryptography, a new entanglement measure, `squashed entanglement', is introduced.
The Modeling Library of Eavesdropping Methods in Quantum Cryptography Protocols by Model Checking
NASA Astrophysics Data System (ADS)
Yang, Fan; Yang, Guowu; Hao, Yujie
2016-07-01
The most crucial issue of quantum cryptography protocols is its security. There exists many ways to attack the quantum communication process. In this paper, we present a model checking method for modeling the eavesdropping in quantum information protocols. So when the security properties of a certain protocol are needed to be verified, we can directly use the models which are already built. Here we adopt the probabilistic model checking tool—PRISM to model these attack methods. The verification results show that the detection rate of eavesdropping is approximately close to 1 when enough photons are transmitted.
The Modeling Library of Eavesdropping Methods in Quantum Cryptography Protocols by Model Checking
NASA Astrophysics Data System (ADS)
Yang, Fan; Yang, Guowu; Hao, Yujie
2016-03-01
The most crucial issue of quantum cryptography protocols is its security. There exists many ways to attack the quantum communication process. In this paper, we present a model checking method for modeling the eavesdropping in quantum information protocols. So when the security properties of a certain protocol are needed to be verified, we can directly use the models which are already built. Here we adopt the probabilistic model checking tool—PRISM to model these attack methods. The verification results show that the detection rate of eavesdropping is approximately close to 1 when enough photons are transmitted.
Timofeev, A. V.; Pomozov, D. I.; Makkaveev, A. P.; Molotkov, S. N.
2007-05-15
Quantum cryptography systems combine two communication channels: a quantum and a classical one. (They can be physically implemented in the same fiber-optic link, which is employed as a quantum channel when one-photon states are transmitted and as a classical one when it carries classical data traffic.) Both channels are supposed to be insecure and accessible to an eavesdropper. Error correction in raw keys, interferometer balancing, and other procedures are performed by using the public classical channel. A discussion of the requirements to be met by the classical channel is presented.
Femtosecond Laser--Pumped Source of Entangled Photons for Quantum Cryptography Applications
Pan, D.; Donaldson, W.; Sobolewski, R.
2007-07-31
We present an experimental setup for generation of entangled-photon pairs via spontaneous parametric down-conversion, based on the femtosecond-pulsed laser. Our entangled-photon source utilizes a 76-MHz-repetition-rate, 100-fs-pulse-width, mode-locked, ultrafast femtosecond laser, which can produce, on average, more photon pairs than a cw laser of an equal pump power. The resulting entangled pairs are counted by a pair of high-quantum-efficiency, single-photon, silicon avalanche photodiodes. Our apparatus is intended as an efficient source/receiver system for the quantum communications and quantum cryptography applications.
Active stabilization of the optical part in fiber optic quantum cryptography
NASA Astrophysics Data System (ADS)
Balygin, K. A.; Klimov, A. N.; Kulik, S. P.; Molotkov, S. N.
2016-03-01
The method of active stabilization of the polarization and other parameters of the optical part of a two-pass fiber optic quantum cryptography has been proposed and implemented. The method allows the completely automated maintenance of the visibility of interference close to an ideal value ( V ≥ 0.99) and the reduction of the instrumental contribution to the error in primary keys (QBER) to 0.5%.
Cryptographic robustness of practical quantum cryptography: BB84 key distribution protocol
Molotkov, S. N.
2008-07-15
In real fiber-optic quantum cryptography systems, the avalanche photodiodes are not perfect, the source of quantum states is not a single-photon one, and the communication channel is lossy. For these reasons, key distribution is impossible under certain conditions for the system parameters. A simple analysis is performed to find relations between the parameters of real cryptography systems and the length of the quantum channel that guarantee secure quantum key distribution when the eavesdropper's capabilities are limited only by fundamental laws of quantum mechanics while the devices employed by the legitimate users are based on current technologies. Critical values are determined for the rate of secure real-time key generation that can be reached under the current technology level. Calculations show that the upper bound on channel length can be as high as 300 km for imperfect photodetectors (avalanche photodiodes) with present-day quantum efficiency ({eta} {approx} 20%) and dark count probability (p{sub dark} {approx} 10{sup -7})
Field test of a practical secure communication network with decoy-state quantum cryptography.
Chen, Teng-Yun; Liang, Hao; Liu, Yang; Cai, Wen-Qi; Ju, Lei; Liu, Wei-Yue; Wang, Jian; Yin, Hao; Chen, Kai; Chen, Zeng-Bing; Peng, Cheng-Zhi; Pan, Jian-Wei
2009-04-13
We present a secure network communication system that operated with decoy-state quantum cryptography in a real-world application scenario. The full key exchange and application protocols were performed in real time among three nodes, in which two adjacent nodes were connected by approximate 20 km of commercial telecom optical fiber. The generated quantum keys were immediately employed and demonstrated for communication applications, including unbreakable real-time voice telephone between any two of the three communication nodes, or a broadcast from one node to the other two nodes by using one-time pad encryption. PMID:19365479
Reduced randomness in quantum cryptography with sequences of qubits encoded in the same basis
Lamoureux, L.-P.; Cerf, N. J.; Bechmann-Pasquinucci, H.; Gisin, N.; Macchiavello, C.
2006-03-15
We consider the cloning of sequences of qubits prepared in the states used in the BB84 or six-state quantum cryptography protocol, and show that the single-qubit fidelity is unaffected even if entire sequences of qubits are prepared in the same basis. This result is only valid provided that the sequences are much shorter than the total key. It is of great importance for practical quantum cryptosystems because it reduces the need for high-speed random number generation without impairing on the security against finite-size cloning attacks.
Information complementarity in multipartite quantum states and security in cryptography
NASA Astrophysics Data System (ADS)
Bera, Anindita; Kumar, Asutosh; Rakshit, Debraj; Prabhu, R.; SenDe, Aditi; Sen, Ujjwal
2016-03-01
We derive complementarity relations for arbitrary quantum states of multiparty systems of any number of parties and dimensions between the purity of a part of the system and several correlation quantities, including entanglement and other quantum correlations as well as classical and total correlations, of that part with the remainder of the system. We subsequently use such a complementarity relation between purity and quantum mutual information in the tripartite scenario to provide a bound on the secret key rate for individual attacks on a quantum key distribution protocol.
Cryptography in the Bounded-Quantum-Storage Model
NASA Astrophysics Data System (ADS)
Schaffner, Christian
2007-09-01
This thesis initiates the study of cryptographic protocols in the bounded-quantum-storage model. On the practical side, simple protocols for Rabin Oblivious Transfer, 1-2 Oblivious Transfer and Bit Commitment are presented. No quantum memory is required for honest players, whereas the protocols can only be broken by an adversary controlling a large amount of quantum memory. The protocols are efficient, non-interactive and can be implemented with today's technology. On the theoretical side, new entropic uncertainty relations involving min-entropy are established and used to prove the security of protocols according to new strong security definitions. For instance, in the realistic setting of Quantum Key Distribution (QKD) against quantum-memory-bounded eavesdroppers, the uncertainty relation allows to prove the security of QKD protocols while tolerating considerably higher error rates compared to the standard model with unbounded adversaries.
On one asymptotic property of time-shift quantum cryptography
NASA Astrophysics Data System (ADS)
Molotkov, S. N.
2009-12-01
One of the basic results of classical information theory is that error-free information transmission is possible even through an imperfect binary communication channel with noise up to an error of Q c = 1/2. There is a fundamental and applied question of whether quantum-mechanical constraints can ensure error-free classical-information transmission with quantum states and, moreover, guarantee the security of distributed keys up to the theoretical limit in the error Q c. It has been shown that the secure key distribution is possible up to the error Q c in the asymptotic limit of a large number of bases.
NASA Astrophysics Data System (ADS)
Jacak, Monika; Jacak, Janusz; Jóźwiak, Piotr; Jóźwiak, Ireneusz
2016-06-01
The overview of the current status of quantum cryptography is given in regard to quantum key distribution (QKD) protocols, implemented both on nonentangled and entangled flying qubits. Two commercial R&D platforms of QKD systems are described (the Clavis II platform by idQuantique implemented on nonentangled photons and the EPR S405 Quelle platform by AIT based on entangled photons) and tested for feasibility of their usage in commercial TELECOM fiber metropolitan networks. The comparison of systems efficiency, stability and resistivity against noise and hacker attacks is given with some suggestion toward system improvement, along with assessment of two models of QKD.
Optimal alphabets for noise-resistant quantum cryptography
NASA Astrophysics Data System (ADS)
Sych, Denis V.; Grishanin, Boris A.; Zadkov, Victor N.
2005-06-01
Possibilities of improving critical error rate of quantum key distribution (QKD) protocols for different strategies of eavesdropping are investigated. QKD-protocols with discrete alphabets letters of which form regular polyhedrons on the Bloch sphere (tetrahedron octahedron cube icosahedron and dodecahedron which have 4, 6, 8, 12 and 20 vertexes respectively) and QKD-protocol with continuous alphabet which corresponds to the limiting case of a polyhedron with infinitive number of vortexes are considered. Stability of such QKD-protocols to the noise in a quantum channel which is due to the Eve's interference that apply either intercept-receipt or optimal eavesdropping strategy at the individual attacks is studied in detail. It is shown that in case of optimal eavesdropping strategy after bases reconciliation the QKD-protocol with continuous alphabet surpasses all other protocols in terms of noise-resistance. Without basis reconciliation the highest critical error rate have the protocol with tetrahedron-type alphabet.
Loss-tolerant quantum cryptography with imperfect sources
NASA Astrophysics Data System (ADS)
Tamaki, Kiyoshi; Curty, Marcos; Kato, Go; Lo, Hoi-Kwong; Azuma, Koji
2014-11-01
In principle, quantum key distribution (QKD) offers unconditional security based on the laws of physics. Unfortunately, all previous QKD experiments assume perfect state preparation in their security analysis. Therefore, the generated key is not proven to be secure in the presence of unavoidable modulation errors. The key reason that modulation errors are not considered in previous QKD experiments lies in a crucial weakness of the standard Gottesman-Lo-Lütkenhaus-Preskill (GLLP) model, namely, it is not loss tolerant and Eve may in principle enhance imperfections through losses. Here, we propose a QKD protocol that is loss tolerant to state preparation flaws. Importantly, we show conclusively that the state preparation process in QKD can be much less precise than initially thought. Our method can also be applied to other quantum cryptographic protocols.
High-Rate Strong-Signal Quantum Cryptography
NASA Technical Reports Server (NTRS)
Yuen, Horace P.
1996-01-01
Several quantum cryptosystems utilizing different kinds of nonclassical lights, which can accommodate high intensity fields and high data rate, are described. However, they are all sensitive to loss and both the high rate and the strong-signal character rapidly disappear. A squeezed light homodyne detection scheme is proposed which, with present-day technology, leads to more than two orders of magnitude data rate improvement over other current experimental systems for moderate loss.
Intermediate states in quantum cryptography and Bell inequalities
Bechmann-Pasquinucci, H.; Gisin, N.
2003-06-01
Intermediate states are known from intercept/resend eavesdropping in the Bennett-Brassard 1984 (BB84) quantum cryptographic protocol. But they also play fundamental roles in the optimal eavesdropping strategy on the BB84 protocol and in the CHSH (Clauser-Horne-Shimony-Holt) inequality. We generalize the intermediate states to an arbitrary dimension and consider intercept/resend eavesdropping, optimal eavesdropping on the generalized BB84 protocol and present a generalized Clauser-Horne-Shimony-Holt inequality for two entangled qudits based on these states.
Memory Attacks on Device-Independent Quantum Cryptography
NASA Astrophysics Data System (ADS)
Barrett, Jonathan; Colbeck, Roger; Kent, Adrian
2013-01-01
Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage, or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defenses include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defenses as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each other (and no other party).
Memory attacks on device-independent quantum cryptography.
Barrett, Jonathan; Colbeck, Roger; Kent, Adrian
2013-01-01
Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage, or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defenses include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defenses as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each other (and no other party). PMID:23383767
Bridging the gap between theory and practice in quantum cryptography
NASA Astrophysics Data System (ADS)
Curty, Marcos; Tamaki, Kiyoshi; Xu, Feihu; Mizutani, Akihiro; Lim, Charles C. W.; Qi, Bing; Lo, Hoi-Kwong
2015-10-01
Quantum key distribution (QKD) needs to close the big gap between theory and practice to be a suitable technology for achieving information-theoretic secure communications. Indeed, recent studies on side-channel attacks have exposed the vulnerabilities of QKD implementations against an eavesdropper who may try to attack both the source and the measurement device. Here, we review two potential approaches that, combined, could bring this goal closer: measurement-device-independent QKD and the loss-tolerant QKD protocol. The former removes all possible side-channels from the measurement apparatus and guarantees a high performance over long distances. The latter appears as a robust solution against typical source flaws and it offers similar key rates as those of standard QKD systems. Most importantly, the feasibility of both solutions has already been demonstrated in several lab and field-test experiments.
NASA Astrophysics Data System (ADS)
Zhang, Yichen; Yu, Song; Guo, Hong
2015-11-01
We propose a modified no-switching continuous-variable quantum key distribution protocol by employing a practical noiseless linear amplifier at the receiver to increase the maximal transmission distance and tolerable excess noise. A security analysis is presented to derive the secure bound of the protocol in presence of a Gaussian noisy lossy channel. Simulation results show that the modified protocol can not only transmit longer distance and tolerate more channel excess noise than the original protocol, but also distribute more secure keys in the enhanced region where we define a critical point to separate the enhanced and degenerative region. This critical point presents the condition of using a practical noiseless linear amplifier in the no-switching continuous-variable quantum cryptography, which is meaningful and instructive to implement a practical experiment.
Acin, Antonio; Gisin, Nicolas; Scarani, Valerio
2004-01-01
We propose a class of quantum cryptography protocols that are robust against photon-number-splitting attacks (PNS) in a weak coherent-pulse implementation. We give a quite exhaustive analysis of several eavesdropping attacks on these schemes. The honest parties (Alice and Bob) use present-day technology, in particular an attenuated laser as an approximation of a single-photon source. The idea of the protocols is to exploit the nonorthogonality of quantum states to decrease the information accessible to Eve due to the multiphoton pulses produced by the imperfect source. The distance at which the key distribution becomes insecure due to the PNS attack is significantly increased compared to the existing schemes. We also show that strong-pulse implementations, where a strong pulse is included as a reference, allow for key distribution robust against photon-number-splitting attacks.
NASA Astrophysics Data System (ADS)
Wang, Wei-Long; Gao, Ming; Ma, Zhi
2013-11-01
The one-way Faraday-Michelson system is a very useful practical quantum cryptography system where Faraday mirrors (FMs) play an important role. In this paper we analyze the security of this system against imperfect FMs. We consider the security loophole caused by imperfect FMs in Alice’s and Bob’s security zones. Then we implement a passive FM attack in this system. By changing the values of the imperfection parameters of Alice’s FMs, we calculate the quantum bit error rate between Alice and Bob induced by Eve and the probability that Eve obtains outcomes successfully. It is shown that the imperfection of one of Alice’s two FMs makes the system sensitive to an attack. Finally we give a modified key rate as a function of the FM imperfections. The security analysis indicates that both Alice’s and Bob’s imperfect FMs can compromise the secure key.
Incoherent and coherent eavesdropping in the six-state protocol of quantum cryptography
NASA Astrophysics Data System (ADS)
Bechmann-Pasquinucci, H.; Gisin, N.
1999-06-01
All incoherent as well as 2- and 3-qubit coherent eavesdropping strategies on the six-state protocol of quantum cryptography are classified. For a disturbance of 1/6, the optimal incoherent eavesdropping strategy reduces to the universal quantum cloning machine. Coherent eavesdropping cannot increase Eve's Shannon information, neither on the entire string of bits, nor on the set of bits received undisturbed by Bob. However, coherent eavesdropping can increase as well Eve's Renyi information as her probability of guessing correctly all bits. The case that Eve delays the measurement of her probe until after the public discussion on error correction and privacy amplification is also considered. It is argued that by doing so, Eve gains only negligibly small additional information.
High-dimensional quantum cryptography with twisted light
NASA Astrophysics Data System (ADS)
Mirhosseini, Mohammad; Magaña-Loaiza, Omar S.; O'Sullivan, Malcolm N.; Rodenburg, Brandon; Malik, Mehul; Lavery, Martin P. J.; Padgett, Miles J.; Gauthier, Daniel J.; Boyd, Robert W.
2015-03-01
Quantum key distribution (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error rates that such a system can tolerate. Here we describe a proof-of-principle experiment that indicates the feasibility of high-dimensional QKD based on the transverse structure of the light field allowing for the transfer of more than 1 bit per photon. Our implementation uses the orbital angular momentum (OAM) of photons and the corresponding mutually unbiased basis of angular position (ANG). Our experiment uses a digital micro-mirror device for the rapid generation of OAM and ANG modes at 4 kHz, and a mode sorter capable of sorting single photons based on their OAM and ANG content with a separation efficiency of 93%. Through the use of a seven-dimensional alphabet encoded in the OAM and ANG bases, we achieve a channel capacity of 2.05 bits per sifted photon. Our experiment demonstrates that, in addition to having an increased information capacity, multilevel QKD systems based on spatial-mode encoding can be more resilient against intercept-resend eavesdropping attacks.
Free-space quantum cryptography in the H-alpha Fraunhofer window
NASA Astrophysics Data System (ADS)
Rogers, D. J.; Bienfang, J. C.; Mink, A.; Hershman, B. J.; Nakassis, A.; Tang, X.; Ma, L.; Su, D. H.; Williams, Carl J.; Clark, Charles W.
2006-08-01
Free-space Quantum key distribution (QKD) has shown the potential for the practical production of cryptographic key for ultra-secure communications. The performance of any QKD system is ultimately limited by the signal to noise ratio on the single-photon channel, and over most useful communications links the resulting key rates are impractical for performing continuous one-time-pad encryption of today's broadband communications. We have adapted clock and data recovery techniques from modern telecommunications practice, combined with a synchronous classical free-space optical communications link operating in parallel, to increase the repetition rate of a free-space QKD system by roughly 2 orders of magnitude over previous demonstrations. We have also designed the system to operate in the H-alpha Fraunhofer window at 656.28 nm, where the solar background is reduced by roughly 7 dB. This system takes advantage of high efficiency silicon single-photon avalanche photodiodes with <50ps timing resolution that are expected to enable operation at a repetition rate of 2.5 GHz. We have identified scalable solutions for delivering sustained one-time-pad encryption at 10 Mbps, thus making it possible to integrate quantum cryptography into first-generation Ethernet protocols.
NASA Astrophysics Data System (ADS)
Jeong, Youn-Chang; Kim, Yong-Su; Kim, Yoon-Ho
2016-01-01
The decoy-state method allows the use of weak coherent pulses in quantum cryptography, and to date, various strategies for the decoy state have been proposed. Here, we experimentally compare the secret key generation rates between the one-decoy and two-decoy implementations of the Bennett-Brassard 1984 (BB84) quantum key distribution protocol through a 3.1-km optical fiber at 780 nm. Once the parameters of the experimental setup are optimized for the maximal secret key generation rate for each implementation, it is found that the two-decoy implementation outperforms the one-decoy implementation.
Security of two quantum cryptography protocols using the same four qubit states
Branciard, Cyril; Gisin, Nicolas; Kraus, Barbara; Scarani, Valerio
2005-09-15
The first quantum cryptography protocol, proposed by Bennett and Brassard in 1984 (BB84), has been widely studied in recent years. This protocol uses four states (more precisely, two complementary bases) for the encoding of the classical bit. Recently, it has been noticed that by using the same four states, but a different encoding of information, one can define a protocol which is more robust in practical implementations, specifically when attenuated laser pulses are used instead of single-photon sources [V. Scarani et al., Phys. Rev. Lett. 92, 057901 (2004), referred to as the SARG04 protocol]. We present a detailed study of SARG04 in two different regimes. In the first part, we consider an implementation with a single-photon source: we derive bounds on the error rate Q for security against all possible attacks by the eavesdropper. The lower and the upper bound obtained for SARG04 (Q < or approx. 10.95% and Q > or approx. 14.9%, respectively) are close to those obtained for BB84 (Q < or approx. 12.4% and Q > or approx. 14.6%, respectively). In the second part, we consider a realistic source consisting of an attenuated laser and improve on previous analysis by allowing Alice to optimize the mean number of photons as a function of the distance. The SARG04 protocol is found to perform better than BB84, both in secret-key rate and in maximal achievable distance, for a wide class of Eve's attacks.
NASA Astrophysics Data System (ADS)
Liang, Chuang
New telecommunication techniques utilizing distinctive quantum properties, e.g., measurement uncertainties and entanglement, extend the capabilities of existing systems. Quantum cryptography, as an example, provides physical layer security enforced by fundamental physical laws, while modern cryptographic techniques rely on assumptions of intractability of certain mathematical problems with limited computational power. Rapid growth of the Internet leading to global telecommunications puts heavy demands on information security. A novel keyed direct data encryption technique based on the fundamental and irreducible quantum noise of laser light is shown to be compatible with the existing high-speed optical communications infrastructure. With this technique, line encryption for OC-12 (622 Mbps) SONET data over 250 km in a wavelength-division-multiplexing network is demonstrated with fully streaming data. Nonlocal correlation is employed in applications including cryptographic key generation whose practical realizations require telecom-band photon counting and entangled photon-pair generation. Existing telecom-band avalanche-photodiode based photon-counting techniques suffer from large detection noise at high operation rates. New techniques such as ultrashort gating and synchronous sampling at the onset of avalanches are introduced for suppressing the detection noise at high operation speeds. Photon counting at record speeds (25 MHz) that employing an avalanche photodiode is developed, demonstrated and deployed in the experimental studies. Telecom-band correlated photons can be directly created inside optical fibers through its chi(3) nonlinearity. This technique brings practical advantages such as the easy compatibility with fiber-optic systems, excellent spatial modal purity, and potential high-speed operation. As a practical development of this technique, a novel Faraday-mirror based ultra-stable scheme for generating polarization entangled photon-pairs is proposed
Kaszlikowski, Dagomir; Lim, J.Y.; Englert, Berthold-Georg; Kwek, L.C.
2005-10-15
The security of a cryptographic key that is generated by communication through a noisy quantum channel relies on the ability to distill a shorter secure key sequence from a longer insecure one. We show that - for protocols that use quantum channels of any dimension and completely characterize them by state tomography - the noise threshold for classical advantage distillation of a specific kind is substantially lower than the threshold for quantum entanglement distillation if the eavesdropper can perform powerful coherent attacks. In marked contrast, earlier investigations had shown that the thresholds are identical for incoherent attacks on the same classical distillation scheme. It remains an open question whether other schemes for classical advantage distillation have higher thresholds for coherent eavesdropping attacks.
NASA Astrophysics Data System (ADS)
Kronberg, D. A.; Molotkov, S. N.
2009-10-01
A new family of two-parameter quantum key distribution protocols is discussed where eavesdropping is detected by using two parameters: bit error rate Q and photon count rate q in control time slots. When a single-photon source is used and mutually orthogonal states are prepared in each basis, the protocol’s maximum tolerable error rate for secure key distribution is the highest, reaching a theoretical upper limit of 50%. When the signal states emitted by the source of attenuated laser light include multiphoton coherent states, the protocol also guarantees secure key distribution over the longest distance as compared to other quantum cryptography systems, up to the channel length for which the channel losses are sufficiently high that all five-photon pulses can be blocked by an eavesdropper.
Orthogonal-state-based cryptography in quantum mechanics and local post-quantum theories
NASA Astrophysics Data System (ADS)
Aravinda, S.; Banerjee, Anindita; Pathak, Anirban; Srikanth, R.
2014-02-01
We introduce the concept of cryptographic reduction, in analogy with a similar concept in computational complexity theory. In this framework, class A of crypto-protocols reduces to protocol class B in a scenario X, if for every instance a of A, there is an instance b of B and a secure transformation X that reproduces a given b, such that the security of b guarantees the security of a. Here we employ this reductive framework to study the relationship between security in quantum key distribution (QKD) and quantum secure direct communication (QSDC). We show that replacing the streaming of independent qubits in a QKD scheme by block encoding and transmission (permuting the order of particles block by block) of qubits, we can construct a QSDC scheme. This forms the basis for the block reduction from a QSDC class of protocols to a QKD class of protocols, whereby if the latter is secure, then so is the former. Conversely, given a secure QSDC protocol, we can of course construct a secure QKD scheme by transmitting a random key as the direct message. Then the QKD class of protocols is secure, assuming the security of the QSDC class which it is built from. We refer to this method of deduction of security for this class of QKD protocols, as key reduction. Finally, we propose an orthogonal-state-based deterministic key distribution (KD) protocol which is secure in some local post-quantum theories. Its security arises neither from geographic splitting of a code state nor from Heisenberg uncertainty, but from post-measurement disturbance.
ERIC Educational Resources Information Center
Hall, Matthew
2003-01-01
Uses cryptography to demonstrate the importance of algebra and the use of technology as an effective real application of mathematics. Explains simple encoding and decoding of messages for student learning of modular arithmetic. This elementary encounter with cryptography along with its historical and modern background serves to motivate student…
ERIC Educational Resources Information Center
Wright, Marie A.
1993-01-01
Cryptography is the science that renders data unintelligible to prevent its unauthorized disclosure or modification. Presents an application of matrices used in linear transformations to illustrate a cryptographic system. An example is provided. (17 references) (MDH)
Niederberger, Armand; Scarani, Valerio; Gisin, Nicolas
2005-04-01
In practical quantum cryptography, the source sometimes produces multiphoton pulses, thus enabling the eavesdropper Eve to perform the powerful photon-number-splitting (PNS) attack. Recently, it was shown by Curty and Luetkenhaus [Phys. Rev. A 69, 042321 (2004)] that the PNS attack is not always the optimal attack when two photons are present: if errors are present in the correlations Alice-Bob and if Eve cannot modify Bob's detection efficiency, Eve gains a larger amount of information using another attack based on a 2{yields}3 cloning machine. In this work, we extend this analysis to all distances Alice-Bob. We identify a new incoherent 2{yields}3 cloning attack which performs better than those described before. Using it, we confirm that, in the presence of errors, Eve's better strategy uses 2{yields}3 cloning attacks instead of the PNS. However, this improvement is very small for the implementations of the Bennett-Brassard 1984 (BB84) protocol. Thus, the existence of these new attacks is conceptually interesting but basically does not change the value of the security parameters of BB84. The main results are valid both for Poissonian and sub-Poissonian sources.
NASA Astrophysics Data System (ADS)
Niederberger, Armand; Scarani, Valerio; Gisin, Nicolas
2005-04-01
In practical quantum cryptography, the source sometimes produces multiphoton pulses, thus enabling the eavesdropper Eve to perform the powerful photon-number-splitting (PNS) attack. Recently, it was shown by Curty and Lütkenhaus [Phys. Rev. A 69, 042321 (2004)] that the PNS attack is not always the optimal attack when two photons are present: if errors are present in the correlations Alice-Bob and if Eve cannot modify Bob’s detection efficiency, Eve gains a larger amount of information using another attack based on a 2→3 cloning machine. In this work, we extend this analysis to all distances Alice-Bob. We identify a new incoherent 2→3 cloning attack which performs better than those described before. Using it, we confirm that, in the presence of errors, Eve’s better strategy uses 2→3 cloning attacks instead of the PNS. However, this improvement is very small for the implementations of the Bennett-Brassard 1984 (BB84) protocol. Thus, the existence of these new attacks is conceptually interesting but basically does not change the value of the security parameters of BB84. The main results are valid both for Poissonian and sub-Poissonian sources.
Faint laser pulses versus a single-photon source in free space quantum cryptography
NASA Astrophysics Data System (ADS)
Molotkov, S. N.; Potapova, T. A.
2016-03-01
In this letter we present estimates for the distance of secret key transmission through free space for three different protocols of quantum key distribution: for BB84 and phase time-coding protocols in the case of a strictly single-photon source, and for the relativistic quantum key distribution protocol in the case of faint laser pulses.
Applications of single-qubit rotations in quantum public-key cryptography
NASA Astrophysics Data System (ADS)
Nikolopoulos, Georgios M.
2008-03-01
We discuss cryptographic applications of single-qubit rotations from the perspective of trapdoor one-way functions and public-key encryption. In particular, we present an asymmetric cryptosystem whose security relies on fundamental principles of quantum physics. A quantum public key is used for the encryption of messages while decryption is possible by means of a classical private key only. The trapdoor one-way function underlying the proposed cryptosystem maps integer numbers to quantum states of a qubit and its inversion can be infeasible by virtue of the Holevo’s theorem.
Private classical capacity with a symmetric side channel and its application to quantum cryptography
NASA Astrophysics Data System (ADS)
Smith, Graeme
2008-08-01
We study the symmetric-side-channel-assisted private capacity of a quantum channel, for which we provide a single-letter formula. This capacity is additive, convex, and, for degradable channels, equal to the unassisted private capacity. While a channel’s (unassisted) capacity for private classical communication may be strictly larger than its quantum capacity, we will show that these capacities are equal for degradable channels, thus demonstrating the equivalence of privacy and quantum coherence in this context. We use these ideas to find new bounds on the key rate of quantum key distribution protocols with one-way classical post-processing. For the Bennett-Brassard 1984 protocol, our results demonstrate that collective attacks are strictly stronger than individual attacks.
Quantum cryptography: individual eavesdropping with the knowledge of the error-correcting protocol
Horoshko, D B
2007-12-31
The quantum key distribution protocol BB84 combined with the repetition protocol for error correction is analysed from the point of view of its security against individual eavesdropping relying on quantum memory. It is shown that the mere knowledge of the error-correcting protocol changes the optimal attack and provides the eavesdropper with additional information on the distributed key. (fifth seminar in memory of d.n. klyshko)
NASA Astrophysics Data System (ADS)
Jacak, Monika; Melniczuk, Damian; Jacak, Janusz; Jóźwiak, Ireneusz; Gruber, Jacek; Jóźwiak, Piotr
2015-02-01
In order to assess the susceptibility of the quantum key distribution (QKD) systems to the hacking attack including simultaneous and frequent system self-decalibrations, we analyze the stability of the QKD transmission organized in two commercially available systems. The first one employs non-entangled photons as flying qubits in the dark quantum channel for communication whereas the second one utilizes the entangled photon pairs to secretly share the cryptographic key. Applying standard methods of the statistical data analysis to the characteristic indicators of the quality of the QKD communication (the raw key exchange rate [RKER] and the quantum bit error rate [QBER]), we have estimated the pace of the self-decalibration of both systems and the repeatability rate in the case of controlled worsening of the dark channel quality.
NASA Astrophysics Data System (ADS)
Gerjuoy, Edward
2005-06-01
The security of messages encoded via the widely used RSA public key encryption system rests on the enormous computational effort required to find the prime factors of a large number N using classical (conventional) computers. In 1994 Peter Shor showed that for sufficiently large N, a quantum computer could perform the factoring with much less computational effort. This paper endeavors to explain, in a fashion comprehensible to the nonexpert, the RSA encryption protocol; the various quantum computer manipulations constituting the Shor algorithm; how the Shor algorithm performs the factoring; and the precise sense in which a quantum computer employing Shor's algorithm can be said to accomplish the factoring of very large numbers with less computational effort than a classical computer. It is made apparent that factoring N generally requires many successive runs of the algorithm. Our analysis reveals that the probability of achieving a successful factorization on a single run is about twice as large as commonly quoted in the literature.
Two-way Gaussian quantum cryptography against coherent attacks in direct reconciliation
NASA Astrophysics Data System (ADS)
Ottaviani, Carlo; Mancini, Stefano; Pirandola, Stefano
2015-12-01
We consider a two-way quantum cryptographic protocol with coherent states assuming direct reconciliation. A detailed security analysis is performed considering a two-mode coherent attack, which represents the residual eavesdropping once the parties have reduced the general attack by applying symmetric random permutations. In this context we provide a general analytical expression for the key rate, discussing the impact of the residual two-mode correlations on the security of the scheme. In particular, we identify the optimal eavesdropping against two-way quantum communication, which is given by a two-mode coherent attack with symmetric and separable correlations.
Continuous-variable quantum cryptography is secure against non-Gaussian attacks.
Grosshans, Frédéric; Cerf, Nicolas J
2004-01-30
A general study of arbitrary finite-size coherent attacks against continuous-variable quantum cryptographic schemes is presented. It is shown that, if the size of the blocks that can be coherently attacked by an eavesdropper is fixed and much smaller than the key size, then the optimal attack for a given signal-to-noise ratio in the transmission line is an individual Gaussian attack. Consequently, non-Gaussian coherent attacks do not need to be considered in the security analysis of such quantum cryptosystems. PMID:14995411
Trojan-horse attacks threaten the security of practical quantum cryptography
NASA Astrophysics Data System (ADS)
Jain, Nitin; Anisimova, Elena; Khan, Imran; Makarov, Vadim; Marquardt, Christoph; Leuchs, Gerd
2014-12-01
A quantum key distribution (QKD) system may be probed by an eavesdropper Eve by sending in bright light from the quantum channel and analyzing the back-reflections. We propose and experimentally demonstrate a setup for mounting such a Trojan-horse attack. We show it in operation against the quantum cryptosystem Clavis2 from ID Quantique, as a proof-of-principle. With just a few back-reflected photons, Eve discerns Bob's (secret) basis choice, and thus the raw key bit in the Scarani-Acín-Ribordy-Gisin 2004 protocol, with higher than 90% probability. This would clearly breach the security of the cryptosystem. Unfortunately, Eve's bright pulses have a side effect of causing a high level of afterpulsing in Bob's single-photon detectors, resulting in a large quantum bit error rate that effectively protects this system from our attack. However, in a Clavis2-like system equipped with detectors with less-noisy but realistic characteristics, an attack strategy with positive leakage of the key would exist. We confirm this by a numerical simulation. Both the eavesdropping setup and strategy can be generalized to attack most of the current QKD systems, especially if they lack proper safeguards. We also propose countermeasures to prevent such attacks.
Decoy-state protocol for quantum cryptography with four different intensities of coherent light
Wang Xiangbin
2005-07-15
We propose an efficient decoy-state protocol for practical quantum key distribution using coherent states. The protocol uses four intensities of different coherent light. A good final key rate is achieved by our protocol with typical parameters of existing practical setups, even with a very low channel transmittance.
NASA Astrophysics Data System (ADS)
Zhou, Ming; Chang, Shoude; Grover, Chander P.
2004-06-01
Further to the optical coding based on fluorescent semiconductor quantum dots (QDs), a concept of using mixtures of multiple single-color QDs for creating highly secret cryptograms based on their absorption/emission properties was demonstrated. The key to readout of the optical codes is a group of excitation lights with the predetermined wavelengths programmed in a secret manner. The cryptograms can be printed on the surfaces of different objects such as valuable documents for security purposes.
Hybrid ququart-encoded quantum cryptography protected by Kochen-Specker contextuality
Cabello, Adan; D'Ambrosio, Vincenzo; Nagali, Eleonora; Sciarrino, Fabio
2011-09-15
Quantum cryptographic protocols based on complementarity are not secure against attacks in which complementarity is imitated with classical resources. The Kochen-Specker (KS) theorem provides protection against these attacks, without requiring entanglement or spatially separated composite systems. We analyze the maximum tolerated noise to guarantee the security of a KS-protected cryptographic scheme against these attacks and describe a photonic realization of this scheme using hybrid ququarts defined by the polarization and orbital angular momentum of single photons.
Advanced techniques for free-space optical quantum cryptography over water
NASA Astrophysics Data System (ADS)
Hill, Alexander D.; Christensen, Bradley; Kwiat, Paul G.
2016-03-01
Free-space quantum key distribution (QKD) over water (e.g., ship to ship) may be limited by ship motion and atmospheric effects, such as mode distortion and beam wander due to turbulence. We report on a technique which reduces noise by excluding spatial modes which are less likely to contain QKD signal photons and experimentally demonstrate an improvement in QKD key generation rates in various noise and turbulence regimes.
Quantifying the leakage of quantum protocols for classical two-party cryptography
NASA Astrophysics Data System (ADS)
Salvail, Louis; Schaffner, Christian; Sotáková, Miroslava
2015-12-01
We study quantum protocols among two distrustful parties. By adopting a rather strict definition of correctness — guaranteeing that honest players obtain their correct outcomes only — we can show that every strictly correct quantum protocol implementing a non-trivial classical primitive necessarily leaks information to a dishonest player. This extends known impossibility results to all non-trivial primitives. We provide a framework for quantifying this leakage and argue that leakage is a good measure for the privacy provided to the players by a given protocol. Our framework also covers the case where the two players are helped by a trusted third party. We show that despite the help of a trusted third party, the players cannot amplify the cryptographic power of any primitive. All our results hold even against quantum honest-but-curious adversaries who honestly follow the protocol but purify their actions and apply a different measurement at the end of the protocol. As concrete examples, we establish lower bounds on the leakage of standard universal two-party primitives such as oblivious transfer.
Quantifying the leakage of quantum protocols for classical two-party cryptography
NASA Astrophysics Data System (ADS)
Salvail, Louis; Schaffner, Christian; Sotáková, Miroslava
2014-12-01
We study quantum protocols among two distrustful parties. By adopting a rather strict definition of correctness — guaranteeing that honest players obtain their correct outcomes only — we can show that every strictly correct quantum protocol implementing a non-trivial classical primitive necessarily leaks information to a dishonest player. This extends known impossibility results to all non-trivial primitives. We provide a framework for quantifying this leakage and argue that leakage is a good measure for the privacy provided to the players by a given protocol. Our framework also covers the case where the two players are helped by a trusted third party. We show that despite the help of a trusted third party, the players cannot amplify the cryptographic power of any primitive. All our results hold even against quantum honest-but-curious adversaries who honestly follow the protocol but purify their actions and apply a different measurement at the end of the protocol. As concrete examples, we establish lower bounds on the leakage of standard universal two-party primitives such as oblivious transfer.
General immunity and superadditivity of two-way Gaussian quantum cryptography
Ottaviani, Carlo; Pirandola, Stefano
2016-01-01
We consider two-way continuous-variable quantum key distribution, studying its security against general eavesdropping strategies. Assuming the asymptotic limit of many signals exchanged, we prove that two-way Gaussian protocols are immune to coherent attacks. More precisely we show the general superadditivity of the two-way security thresholds, which are proven to be higher than the corresponding one-way counterparts in all cases. We perform the security analysis first reducing the general eavesdropping to a two-mode coherent Gaussian attack, and then showing that the superadditivity is achieved by exploiting the random on/off switching of the two-way quantum communication. This allows the parties to choose the appropriate communication instances to prepare the key, accordingly to the tomography of the quantum channel. The random opening and closing of the circuit represents, in fact, an additional degree of freedom allowing the parties to convert, a posteriori, the two-mode correlations of the eavesdropping into noise. The eavesdropper is assumed to have no access to the on/off switching and, indeed, cannot adapt her attack. We explicitly prove that this mechanism enhances the security performance, no matter if the eavesdropper performs collective or coherent attacks. PMID:26928053
General immunity and superadditivity of two-way Gaussian quantum cryptography
NASA Astrophysics Data System (ADS)
Ottaviani, Carlo; Pirandola, Stefano
2016-03-01
We consider two-way continuous-variable quantum key distribution, studying its security against general eavesdropping strategies. Assuming the asymptotic limit of many signals exchanged, we prove that two-way Gaussian protocols are immune to coherent attacks. More precisely we show the general superadditivity of the two-way security thresholds, which are proven to be higher than the corresponding one-way counterparts in all cases. We perform the security analysis first reducing the general eavesdropping to a two-mode coherent Gaussian attack, and then showing that the superadditivity is achieved by exploiting the random on/off switching of the two-way quantum communication. This allows the parties to choose the appropriate communication instances to prepare the key, accordingly to the tomography of the quantum channel. The random opening and closing of the circuit represents, in fact, an additional degree of freedom allowing the parties to convert, a posteriori, the two-mode correlations of the eavesdropping into noise. The eavesdropper is assumed to have no access to the on/off switching and, indeed, cannot adapt her attack. We explicitly prove that this mechanism enhances the security performance, no matter if the eavesdropper performs collective or coherent attacks.
General immunity and superadditivity of two-way Gaussian quantum cryptography.
Ottaviani, Carlo; Pirandola, Stefano
2016-01-01
We consider two-way continuous-variable quantum key distribution, studying its security against general eavesdropping strategies. Assuming the asymptotic limit of many signals exchanged, we prove that two-way Gaussian protocols are immune to coherent attacks. More precisely we show the general superadditivity of the two-way security thresholds, which are proven to be higher than the corresponding one-way counterparts in all cases. We perform the security analysis first reducing the general eavesdropping to a two-mode coherent Gaussian attack, and then showing that the superadditivity is achieved by exploiting the random on/off switching of the two-way quantum communication. This allows the parties to choose the appropriate communication instances to prepare the key, accordingly to the tomography of the quantum channel. The random opening and closing of the circuit represents, in fact, an additional degree of freedom allowing the parties to convert, a posteriori, the two-mode correlations of the eavesdropping into noise. The eavesdropper is assumed to have no access to the on/off switching and, indeed, cannot adapt her attack. We explicitly prove that this mechanism enhances the security performance, no matter if the eavesdropper performs collective or coherent attacks. PMID:26928053
A monogamy-of-entanglement game with applications to device-independent quantum cryptography
NASA Astrophysics Data System (ADS)
Tomamichel, Marco; Fehr, Serge; Kaniewski, Jędrzej; Wehner, Stephanie
2013-10-01
We consider a game in which two separate laboratories collaborate to prepare a quantum system and are then asked to guess the outcome of a measurement performed by a third party in a random basis on that system. Intuitively, by the uncertainty principle and the monogamy of entanglement, the probability that both players simultaneously succeed in guessing the outcome correctly is bounded. We are interested in the question of how the success probability scales when many such games are performed in parallel. We show that any strategy that maximizes the probability to win every game individually is also optimal for the parallel repetition of the game. Our result implies that the optimal guessing probability can be achieved without the use of entanglement. We explore several applications of this result. Firstly, we show that it implies security for standard BB84 quantum key distribution when the receiving party uses fully untrusted measurement devices, i.e. we show that BB84 is one-sided device independent. Secondly, we show how our result can be used to prove security of a one-round position-verification scheme. Finally, we generalize a well-known uncertainty relation for the guessing probability to quantum side information.
NASA Astrophysics Data System (ADS)
Kwon, Osung; Lee, Min-Soo; Woo, Min Ki; Park, Byung Kwon; Kim, Il Young; Kim, Yong-Su; Han, Sang-Wook; Moon, Sung
2015-12-01
We characterized a polarization-independent phase modulation method, called double phase modulation, for a practical plug and play quantum key distribution (QKD) system. Following investigation of theoretical backgrounds, we applied the method to the practical QKD system and characterized the performance through comparing single phase modulation (SPM) and double phase modulation. Consequently, we obtained repeatable and accurate phase modulation confirmed by high visibility single photon interference even for input signals with arbitrary polarization. Further, the results show that only 80% of the bias voltage required in the case of single phase modulation is needed to obtain the target amount of phase modulation.
NASA Astrophysics Data System (ADS)
Ray, Megan R.; van Enk, S. J.
2013-10-01
In continuous-variable quantum information processing, detectors are necessarily coarse grained and of finite range. We discuss how, especially, the latter feature is a bug and may easily lead to overoptimistic estimates of entanglement and of security when missed data outside the detector range are ignored. We demonstrate that a straightforward worst-case analysis is sufficient to avoid false positive statements about entanglement. We show that, for our worst-case analysis, entropic separability or security criteria are much superior to variance-based criteria.
Cryptographic robustness of a quantum cryptography system using phase-time coding
Molotkov, S. N.
2008-01-15
A cryptographic analysis is presented of a new quantum key distribution protocol using phase-time coding. An upper bound is obtained for the error rate that guarantees secure key distribution. It is shown that the maximum tolerable error rate for this protocol depends on the counting rate in the control time slot. When no counts are detected in the control time slot, the protocol guarantees secure key distribution if the bit error rate in the sifted key does not exceed 50%. This protocol partially discriminates between errors due to system defects (e.g., imbalance of a fiber-optic interferometer) and eavesdropping. In the absence of eavesdropping, the counts detected in the control time slot are not caused by interferometer imbalance, which reduces the requirements for interferometer stability.
Tripartite counterfactual quantum cryptography
NASA Astrophysics Data System (ADS)
Salih, Hatim
2014-07-01
We show how two distrustful parties, "Bob" and "Charlie," can share a secret key with the help of a mutually trusted "Alice" counterfactually; that is, with no information-carrying particles traveling between any of the three.
ERIC Educational Resources Information Center
Bachman, Dale J.; Brown, Ezra A.; Norton, Anderson H.
2010-01-01
Cryptography is the science of hidden or secret writing. More generally, cryptography refers to the science of safeguarding information. Cryptography allows people to use a public medium such as the Internet to transmit private information securely, thus enabling a whole range of conveniences, from online shopping to personally printed movie…
Popescu-Rohrlich correlations imply efficient instantaneous nonlocal quantum computation
NASA Astrophysics Data System (ADS)
Broadbent, Anne
2016-08-01
In instantaneous nonlocal quantum computation, two parties cooperate in order to perform a quantum computation on their joint inputs, while being restricted to a single round of simultaneous communication. Previous results showed that instantaneous nonlocal quantum computation is possible, at the cost of an exponential amount of prior shared entanglement (in the size of the input). Here, we show that a linear amount of entanglement suffices, (in the size of the computation), as long as the parties share nonlocal correlations as given by the Popescu-Rohrlich box. This means that communication is not required for efficient instantaneous nonlocal quantum computation. Exploiting the well-known relation to position-based cryptography, our result also implies the impossibility of secure position-based cryptography against adversaries with nonsignaling correlations. Furthermore, our construction establishes a quantum analog of the classical communication complexity collapse under nonsignaling correlations.
Heid, Matthias; Luetkenhaus, Norbert
2006-05-15
We investigate the performance of a continuous-variable quantum key distribution scheme in a practical setting. More specifically, we take a nonideal error reconciliation procedure into account. The quantum channel connecting the two honest parties is assumed to be lossy but noiseless. Secret key rates are given for the case that the measurement outcomes are postselected or a reverse reconciliation scheme is applied. The reverse reconciliation scheme loses its initial advantage in the practical setting. If one combines postselection with reverse reconciliation, however, much of this advantage can be recovered.
ERIC Educational Resources Information Center
Tapson, Frank
1996-01-01
Describes public key cryptography, also known as RSA, which is a system using two keys, one used to put a message into cipher and another used to decipher the message. Presents examples using small prime numbers. (MKR)
Neural cryptography with feedback
NASA Astrophysics Data System (ADS)
Ruttor, Andreas; Kinzel, Wolfgang; Shacham, Lanir; Kanter, Ido
2004-04-01
Neural cryptography is based on a competition between attractive and repulsive stochastic forces. A feedback mechanism is added to neural cryptography which increases the repulsive forces. Using numerical simulations and an analytic approach, the probability of a successful attack is calculated for different model parameters. Scaling laws are derived which show that feedback improves the security of the system. In addition, a network with feedback generates a pseudorandom bit sequence which can be used to encrypt and decrypt a secret message.
Molotkov, S. N.
2012-12-15
Any key-generation session contains a finite number of quantum-state messages, and it is there-fore important to understand the fundamental restrictions imposed on the minimal length of a string required to obtain a secret key with a specified length. The entropy uncertainty relations for smooth min and max entropies considerably simplify and shorten the proof of security. A proof of security of quantum key distribution with phase-temporal encryption is presented. This protocol provides the maximum critical error compared to other protocols up to which secure key distribution is guaranteed. In addition, unlike other basic protocols (of the BB84 type), which are vulnerable with respect to an attack by 'blinding' of avalanche photodetectors, this protocol is stable with respect to such an attack and guarantees key security.
Chaos Cryptography with Dynamical Systems
NASA Astrophysics Data System (ADS)
Anderson, Robert; Morse, Jack; Schimmrigk, Rolf
2001-11-01
Cryptography is a subject that draws strength from an amazing variety of different mathematical fields, including such deep results as the Weil-Dwork-Deligne theorem on the zeta function. Physical theories have recently entered the subject as well, an example being the subject of quantum cryptography, motivated in part by Shor's insight into the vulnerability of prime number factorization based crypto systems. In this contribution we describe a cryptographic algorithm which is based on the dynamics of a class of physical models that exhibit chaotic behavior. More precisely, we consider dissipative systems which are described by nonlinear three-dimensional systems of differential equations with strange attractor surfaces of non-integer Lyapunov dimension. The time evolution of such systems in part of the moduli space shows unpredictable behavior, which suggests that they might be useful as pseudorandom number generators. We will show that this is indeed the case and illustrate our procedure mainly with the Lorenz attractor, though we also briefly mention the Rössler system. We use this class of nonlinear models to construct an extremely fast stream cipher with a large keyspace, which we test with Marsaglia's battery of DieHard tests.
NASA Astrophysics Data System (ADS)
Jiang, Mu-Sheng; Sun, Shi-Hai; Tang, Guang-Zhao; Ma, Xiang-Chun; Li, Chun-Yan; Liang, Lin-Mei
2013-12-01
Thanks to the high-speed self-differencing single-photon detector (SD-SPD), the secret key rate of quantum key distribution (QKD), which can, in principle, offer unconditionally secure private communications between two users (Alice and Bob), can exceed 1 Mbit/s. However, the SD-SPD may contain loopholes, which can be exploited by an eavesdropper (Eve) to hack into the unconditional security of the high-speed QKD systems. In this paper, we analyze the fact that the SD-SPD can be remotely controlled by Eve in order to spy on full information without being discovered, then proof-of-principle experiments are demonstrated. Here, we point out that this loophole is introduced directly by the operating principle of the SD-SPD, thus, it cannot be removed, except for the fact that some active countermeasures are applied by the legitimate parties.
Quantum Cryptography II: How to re-use a one-time pad safely even if P=NP.
Bennett, Charles H; Brassard, Gilles; Breidbart, Seth
2014-01-01
When elementary quantum systems, such as polarized photons, are used to transmit digital information, the uncertainty principle gives rise to novel cryptographic phenomena unachievable with traditional transmission media, e.g. a communications channel on which it is impossible in principle to eavesdrop without a high probability of being detected. With such a channel, a one-time pad can safely be reused many times as long as no eavesdrop is detected, and, planning ahead, part of the capacity of these uncompromised transmissions can be used to send fresh random bits with which to replace the one-time pad when an eavesdrop finally is detected. Unlike other schemes for stretching a one-time pad, this scheme does not depend on complexity-theoretic assumptions such as the difficulty of factoring. PMID:25400534
Indirect visual cryptography scheme
NASA Astrophysics Data System (ADS)
Yang, Xiubo; Li, Tuo; Shi, Yishi
2015-10-01
Visual cryptography (VC), a new cryptographic scheme for image. Here in encryption, image with message is encoded to be N sub-images and any K sub-images can decode the message in a special rules (N>=2, 2<=K<=N). Then any K of the N sub-images are printed on transparency and stacked exactly, the message of original image will be decrypted by human visual system, but any K-1 of them get no information about it. This cryptographic scheme can decode concealed images without any cryptographic computations, and it has high security. But this scheme lacks of hidden because of obvious feature of sub-images. In this paper, we introduce indirect visual cryptography scheme (IVCS), which encodes sub-images to be pure phase images without visible strength based on encoding of visual cryptography. The pure phase image is final ciphertexts. Indirect visual cryptography scheme not only inherits the merits of visual cryptography, but also raises indirection, hidden and security. Meanwhile, the accuracy alignment is not required any more, which leads to the strong anti-interference capacity and robust in this scheme. System of decryption can be integrated highly and operated conveniently, and its process of decryption is dynamic and fast, which all lead to the good potentials in practices.
NASA Astrophysics Data System (ADS)
Poon, Ting-Chung
2004-01-01
We introduce a technique called optical scanning cryptography (OSC). The technique can perform encryption on-the-fly using laser beams and can be implemented using an optical heterodyne scanning. We shall first describe the optical heterodyne scanning system and then provide some computer simulations to clarify and confirm the idea of encryption and decryption.
Dynamics of neural cryptography
Ruttor, Andreas; Kinzel, Wolfgang; Kanter, Ido
2007-05-15
Synchronization of neural networks has been used for public channel protocols in cryptography. In the case of tree parity machines the dynamics of both bidirectional synchronization and unidirectional learning is driven by attractive and repulsive stochastic forces. Thus it can be described well by a random walk model for the overlap between participating neural networks. For that purpose transition probabilities and scaling laws for the step sizes are derived analytically. Both these calculations as well as numerical simulations show that bidirectional interaction leads to full synchronization on average. In contrast, successful learning is only possible by means of fluctuations. Consequently, synchronization is much faster than learning, which is essential for the security of the neural key-exchange protocol. However, this qualitative difference between bidirectional and unidirectional interaction vanishes if tree parity machines with more than three hidden units are used, so that those neural networks are not suitable for neural cryptography. In addition, the effective number of keys which can be generated by the neural key-exchange protocol is calculated using the entropy of the weight distribution. As this quantity increases exponentially with the system size, brute-force attacks on neural cryptography can easily be made unfeasible.
Cryptography in a communication system
NASA Astrophysics Data System (ADS)
Best, M. R.
1982-10-01
Communication system protection by cryptography is reviewed. Privacy and authentication problems are discussed. Conventional cryptographic systems as well as public key systems are complementary. Classical security methods such as signed contracts, physical locks, passwords and keys remain important.
Visual cryptography by use of polarization
NASA Astrophysics Data System (ADS)
Yamamoto, Hirotsugu; Imagawa, Takanori; Suyama, Shiro
2010-01-01
Visual cryptography is a powerful method to share secret information, such as identification numbers, between plural members. There have been many papers on visual cryptography by use of intensity modulation. Although the use of intensity modulation is suitable for printing, degradation of image quality is a problem. Another problem for conventional visual cryptography is a risk of theft of physical keys. To cope with these problems, we propose a new field of visual cryptography by use of polarization. In this study, we have implemented polarization decoding by stacking films. Use of polarization processing improves image quality of visual cryptography. The purpose of this paper is to construct visual cryptography based on polarization processing. Furthermore, we construct a new type of visual cryptography that uses stacking order as a key for decryption. The use of stacking order multiplies the complexity of encryption. Then, it is effective to prevent secret against theft because the theft cannot determine the secret only by collecting encrypted films.
Finding Cryptography in Object Code
Jason L. Wright
2008-10-01
Finding and identifying Cryptography is a growing concern in the malware analysis community. In this paper, a heuristic method for determining the likelihood that a given function contains a cryptographic algorithm is discussed and the results of applying this method in various environments is shown. The algorithm is based on frequency analysis of opcodes that make up each function within a binary.
Cryptography as a Pedagogical Tool
ERIC Educational Resources Information Center
Kaur, Manmohan
2008-01-01
In order to get undergraduates interested in mathematics, it is necessary to motivate them, give them good reasons to spend time on a subject that requires hard work, and, if possible, involve them in undergraduate research. This article discusses how cryptography can be used for all these purposes. In particular, a special topics course on…
Practicality of quantum information processing
NASA Astrophysics Data System (ADS)
Lau, Hoi-Kwan
Quantum Information Processing (QIP) is expected to bring revolutionary enhancement to various technological areas. However, today's QIP applications are far from being practical. The problem involves both hardware issues, i.e., quantum devices are imperfect, and software issues, i.e., the functionality of some QIP applications is not fully understood. Aiming to improve the practicality of QIP, in my PhD research I have studied various topics in quantum cryptography and ion trap quantum computation. In quantum cryptography, I first studied the security of position-based quantum cryptography (PBQC). I discovered a wrong assumption in the previous literature that the cheaters are not allowed to share entangled resources. I proposed entanglement attacks that could cheat all known PBQC protocols. I also studied the practicality of continuous-variable (CV) quantum secret sharing (QSS). While the security of CV QSS was considered by the literature only in the limit of infinite squeezing, I found that finitely squeezed CV resources could also provide finite secret sharing rate. Our work relaxes the stringent resources requirement of implementing QSS. In ion trap quantum computation, I studied the phase error of quantum information induced by dc Stark effect during ion transportation. I found an optimized ion trajectory for which the phase error is the minimum. I also defined a threshold speed, above which ion transportation would induce significant error. In addition, I proposed a new application for ion trap systems as universal bosonic simulators (UBS). I introduced two architectures, and discussed their respective strength and weakness. I illustrated the implementations of bosonic state initialization, transformation, and measurement by applying radiation fields or by varying the trap potential. When comparing with conducting optical experiments, the ion trap UBS is advantageous in higher state initialization efficiency and higher measurement accuracy. Finally, I
Secure quantum key distribution
NASA Astrophysics Data System (ADS)
Lo, Hoi-Kwong; Curty, Marcos; Tamaki, Kiyoshi
2014-08-01
Secure communication is crucial in the Internet Age, and quantum mechanics stands poised to revolutionize cryptography as we know it today. In this Review, we introduce the motivation and the current state of the art of research in quantum cryptography. In particular, we discuss the present security model together with its assumptions, strengths and weaknesses. After briefly introducing recent experimental progress and challenges, we survey the latest developments in quantum hacking and countermeasures against it.
Cryptography and system state estimation using polarization states
NASA Astrophysics Data System (ADS)
Kak, Subhash; Verma, Pramode; MacDonald, Greg
2011-09-01
We present new results on cryptography and system state estimation using polarization states of photons. Current quantum cryptography applications are based on the BB84 protocol which is not secure against photon siphoning attacks. Recent research has established that the information that can be obtained from a pure state in repeated experiments is potentially infinite. This can be harnessed by sending a burst of photons confined to a very narrow time window, each such burst containing several bits of information. The proposed method represents a new way of transmitting secret information. While polarization shift-keying methods have been proposed earlier, our method is somewhat different in that it proposes to discover the polarization state of identical photons in a burst from a laser which codes binary information. We also present results on estimating the state of a system based on the polarization of the received photons which can have applications in intrusion detection.
Cryptography with DNA binary strands.
Leier, A; Richter, C; Banzhaf, W; Rauhe, H
2000-06-01
Biotechnological methods can be used for cryptography. Here two different cryptographic approaches based on DNA binary strands are shown. The first approach shows how DNA binary strands can be used for steganography, a technique of encryption by information hiding, to provide rapid encryption and decryption. It is shown that DNA steganography based on DNA binary strands is secure under the assumption that an interceptor has the same technological capabilities as sender and receiver of encrypted messages. The second approach shown here is based on steganography and a method of graphical subtraction of binary gel-images. It can be used to constitute a molecular checksum and can be combined with the first approach to support encryption. DNA cryptography might become of practical relevance in the context of labelling organic and inorganic materials with DNA 'barcodes'. PMID:10963862
Report of the Public Cryptography Study Group.
ERIC Educational Resources Information Center
American Council on Education, Washington, DC.
Concerns of the National Security Agency (NSA) that information contained in some articles about cryptography in learned and professional journals and in monographs might be inimical to the national security are addressed. The Public Cryptography Study Group, with one dissenting opinion, recommends that a voluntary system of prior review of…
Arithmetic for Public-Key Cryptography
NASA Astrophysics Data System (ADS)
Sakiyama, Kazuo; Batina, Lejla
In this chapter, we discuss arithmetic algorithms used for implementing public-key cryptography (PKC). More precisely, we explore the various algorithms for RSA exponentiation and point/divisor multiplication for curve-based cryptography. The selection of the algorithms has a profound impact on the trade-off between cost, performance, and security. The goal of this chapter is to introduce the different recoding techniques to reduce the number of computations efficiently.
Eavesdropping without quantum memory
Bechmann-Pasquinucci, H.
2006-04-15
In quantum cryptography the optimal eavesdropping strategy requires that the eavesdropper uses ancillas and quantum memories in order to optimize her information. What happens if the eavesdropper has no quantum memory? It is shown that in this case the eavesdropper obtains a better information/disturbance trade-off by adopting the simple intercept/resend strategy.
Cryptographie quantique à variables continues
NASA Astrophysics Data System (ADS)
Bencheikh, K.; Jankovic, A.; Symul, T.; Levenson, J. A.
2002-06-01
Nous avons élaboré un protocole de cryptographie quantique qui permet de générer et de distribuer une clé secrète aléatoire. Le protocole repose sur l'utilisation de paires de champs électromagnétiques dont les quadratures présentent des corrélations quantiques de type Einstein-Podolsky-Rosen. Les fluctuations quantiques instantanése constituent les bits aléatoires de la clé secrète, et la dégradation irréversible des corrélations quantiques des quadratures causée par une tierce personne permet de la détecter et de garantir la sécurité d'échange.
Genetic attack on neural cryptography
Ruttor, Andreas; Kinzel, Wolfgang; Naeh, Rivka; Kanter, Ido
2006-03-15
Different scaling properties for the complexity of bidirectional synchronization and unidirectional learning are essential for the security of neural cryptography. Incrementing the synaptic depth of the networks increases the synchronization time only polynomially, but the success of the geometric attack is reduced exponentially and it clearly fails in the limit of infinite synaptic depth. This method is improved by adding a genetic algorithm, which selects the fittest neural networks. The probability of a successful genetic attack is calculated for different model parameters using numerical simulations. The results show that scaling laws observed in the case of other attacks hold for the improved algorithm, too. The number of networks needed for an effective attack grows exponentially with increasing synaptic depth. In addition, finite-size effects caused by Hebbian and anti-Hebbian learning are analyzed. These learning rules converge to the random walk rule if the synaptic depth is small compared to the square root of the system size.
Quantum computing with trapped ions
Hughes, R.J.
1998-01-01
The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.
Neural Network Approach to Locating Cryptography in Object Code
Jason L. Wright; Milos Manic
2009-09-01
Finding and identifying cryptography is a growing concern in the malware analysis community. In this paper, artificial neural networks are used to classify functional blocks from a disassembled program as being either cryptography related or not. The resulting system, referred to as NNLC (Neural Net for Locating Cryptography) is presented and results of applying this system to various libraries are described.
Harry Potter and the Cryptography with Matrices
ERIC Educational Resources Information Center
Chua, Boon Liang
2006-01-01
This article describes Cryptography, defined as the science of encrypting and deciphering messages written in secret codes, it has played a vital role in securing information since ancient times. There are several cryptographic techniques and many make extensive use of mathematics to secure information. The author discusses an activity built…
Report on Pairing-based Cryptography
Moody, Dustin; Peralta, Rene; Perlner, Ray; Regenscheid, Andrew; Roginsky, Allen; Chen, Lily
2015-01-01
This report summarizes study results on pairing-based cryptography. The main purpose of the study is to form NIST’s position on standardizing and recommending pairing-based cryptography schemes currently published in research literature and standardized in other standard bodies. The report reviews the mathematical background of pairings. This includes topics such as pairing-friendly elliptic curves and how to compute various pairings. It includes a brief introduction to existing identity-based encryption (IBE) schemes and other cryptographic schemes using pairing technology. The report provides a complete study of the current status of standard activities on pairing-based cryptographic schemes. It explores different application scenarios for pairing-based cryptography schemes. As an important aspect of adopting pairing-based schemes, the report also considers the challenges inherent in validation testing of cryptographic algorithms and modules. Based on the study, the report suggests an approach for including pairing-based cryptography schemes in the NIST cryptographic toolkit. The report also outlines several questions that will require further study if this approach is followed. PMID:26958435
Number Theory and Public-Key Cryptography.
ERIC Educational Resources Information Center
Lefton, Phyllis
1991-01-01
Described are activities in the study of techniques used to conceal the meanings of messages and data. Some background information and two BASIC programs that illustrate the algorithms used in a new cryptographic system called "public-key cryptography" are included. (CW)
Report on Pairing-based Cryptography.
Moody, Dustin; Peralta, Rene; Perlner, Ray; Regenscheid, Andrew; Roginsky, Allen; Chen, Lily
2015-01-01
This report summarizes study results on pairing-based cryptography. The main purpose of the study is to form NIST's position on standardizing and recommending pairing-based cryptography schemes currently published in research literature and standardized in other standard bodies. The report reviews the mathematical background of pairings. This includes topics such as pairing-friendly elliptic curves and how to compute various pairings. It includes a brief introduction to existing identity-based encryption (IBE) schemes and other cryptographic schemes using pairing technology. The report provides a complete study of the current status of standard activities on pairing-based cryptographic schemes. It explores different application scenarios for pairing-based cryptography schemes. As an important aspect of adopting pairing-based schemes, the report also considers the challenges inherent in validation testing of cryptographic algorithms and modules. Based on the study, the report suggests an approach for including pairing-based cryptography schemes in the NIST cryptographic toolkit. The report also outlines several questions that will require further study if this approach is followed. PMID:26958435
Cryptography and the Internet: lessons and challenges
McCurley, K.S.
1996-12-31
The popularization of the Internet has brought fundamental changes to the world, because it allows a universal method of communication between computers. This carries enormous benefits with it, but also raises many security considerations. Cryptography is a fundamental technology used to provide security of computer networks, and there is currently a widespread engineering effort to incorporate cryptography into various aspects of the Internet. The system-level engineering required to provide security services for the Internet carries some important lessons for researchers whose study is focused on narrowly defined problems. It also offers challenges to the cryptographic research community by raising new questions not adequately addressed by the existing body of knowledge. This paper attempts to summarize some of these lessons and challenges for the cryptographic research community.
Asymmetric cryptography based on wavefront sensing
NASA Astrophysics Data System (ADS)
Peng, Xiang; Wei, Hengzheng; Zhang, Peng
2006-12-01
A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.
Asymmetric cryptography based on wavefront sensing.
Peng, Xiang; Wei, Hengzheng; Zhang, Peng
2006-12-15
A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments. PMID:17130909
Nonequivalence of two flavors of oblivious transfer at the quantum level
He Guangping; Wang, Z. D.
2006-04-15
Though all-or-nothing oblivious transfer and one-out-of-two oblivious transfer are equivalent in classical cryptography, we here show that a protocol built upon secure quantum all-or-nothing oblivious transfer cannot satisfy the rigorous definition of quantum one-out-of-two oblivious transfer due to the nature of quantum cryptography. Thus the securities of the two oblivious transfer protocols are not equivalent at the quantum level.
Device-independent two-party cryptography secure against sequential attacks
NASA Astrophysics Data System (ADS)
Kaniewski, Jędrzej; Wehner, Stephanie
2016-05-01
The goal of two-party cryptography is to enable two parties, Alice and Bob, to solve common tasks without the need for mutual trust. Examples of such tasks are private access to a database, and secure identification. Quantum communication enables security for all of these problems in the noisy-storage model by sending more signals than the adversary can store in a certain time frame. Here, we initiate the study of device-independent (DI) protocols for two-party cryptography in the noisy-storage model. Specifically, we present a relatively easy to implement protocol for a cryptographic building block known as weak string erasure and prove its security even if the devices used in the protocol are prepared by the dishonest party. DI two-party cryptography is made challenging by the fact that Alice and Bob do not trust each other, which requires new techniques to establish security. We fully analyse the case of memoryless devices (for which sequential attacks are optimal) and the case of sequential attacks for arbitrary devices. The key ingredient of the proof, which might be of independent interest, is an explicit (and tight) relation between the violation of the Clauser–Horne–Shimony–Holt inequality observed by Alice and Bob and uncertainty generated by Alice against Bob who is forced to measure his system before finding out Alice’s setting (guessing with postmeasurement information). In particular, we show that security is possible for arbitrarily small violation.
Resource Letter QI-1: Quantum Information
NASA Astrophysics Data System (ADS)
Strauch, Frederick W.
2016-07-01
This Resource Letter surveys the history and modern developments in the field of quantum information. It is written to guide advanced undergraduates, beginning graduate students, and other new researchers to the theoretical and experimental aspects of this field. The topics covered include quantum states and processes, quantum coding and cryptography, quantum computation, the experimental implementation of quantum information processing, and the role of quantum information in the fundamental properties and foundations of physical theories.
Comparative Analysis of Cryptography Library in IoT
NASA Astrophysics Data System (ADS)
Kumar, Uday; Borgohain, Tuhin; Sanyal, Sugata
2015-05-01
The paper aims to do a survey along with a comparative analysis of the various cryptography libraries that are applicable in the field of Internet of Things (IoT). The first half of the paper briefly introduces the various cryptography libraries available in the field of cryptography along with a list of all the algorithms contained within the libraries. The second half of the paper deals with cryptography libraries specifically aimed for application in the field of Internet of Things. The various libraries and their performance analysis listed down in this paper are consolidated from various sources with the aim of providing a single comprehensive repository for reference to the various cryptography libraries and the comparative analysis of their features in IoT.
Quantum tagging for tags containing secret classical data
Kent, Adrian
2011-08-15
Various authors have considered schemes for quantum tagging, that is, authenticating the classical location of a classical tagging device by sending and receiving quantum signals from suitably located distant sites, in an environment controlled by an adversary whose quantum information processing and transmitting power is potentially unbounded. All of the schemes proposed elsewhere in the literature assume that the adversary is able to inspect the interior of the tagging device. All of these schemes have been shown to be breakable if the adversary has unbounded predistributed entanglement. We consider here the case in which the tagging device contains a finite key string shared with distant sites but kept secret from the adversary, and show this allows the location of the tagging device to be authenticated securely and indefinitely. Our protocol relies on quantum key distribution between the tagging device and at least one distant site, and demonstrates a new practical application of quantum key distribution. It also illustrates that the attainable security in position-based cryptography can depend crucially on apparently subtle details in the security scenario considered.
Comment on "Cheating prevention in visual cryptography".
Chen, Yu-Chi; Horng, Gwoboa; Tsai, Du-Shiau
2012-07-01
Visual cryptography (VC), proposed by Naor and Shamir, has numerous applications, including visual authentication and identification, steganography, and image encryption. In 2006, Horng showed that cheating is possible in VC, where some participants can deceive the remaining participants by forged transparencies. Since then, designing cheating-prevention visual secret-sharing (CPVSS) schemes has been studied by many researchers. In this paper, we cryptanalyze the Hu-Tzeng CPVSS scheme and show that it is not cheating immune. We also outline an improvement that helps to overcome the problem. PMID:22410333
Evaluation of correlation in optical encryption by using visual cryptography
NASA Astrophysics Data System (ADS)
Yi, Sang-Yi; Ryu, Chung-Sang; Ryu, Dae-Hyun; Lee, Seung-Hyun
2001-03-01
Visual cryptography made it possible to decrypt the information encrypted by thresholding scheme not with digital system but with human vision system. This method, however, has some limit in it because of the rack of resolution in both the spatial and amplitude domain. Optical visual cryptography, which used laser system instead of human eyesight, was proposed by conjunction of the optical theory with the cryptography. However, it also had some difficulties because it did not overcome the existing problem of visual cryptography completely. The problems occurred in the process of transferring data processing system from visual to optics. Therefore, it is appropriate to approach these problems in terms of optics. The results show that the optical visual cryptograph system has both the effectiveness and reliability as well as real-time implementation property.
Counterfactual attack on counterfactual quantum key distribution
NASA Astrophysics Data System (ADS)
Zhang, Sheng; Wnang, Jian; Tang, Chao Jing
2012-05-01
It is interesting that counterfactual quantum cryptography protocols allow two remotely separated parties to share a secret key without transmitting any signal particles. Generally, these protocols, expected to provide security advantages, base their security on a translated no-cloning theorem. Therefore, they potentially exhibit unconditional security in theory. In this letter, we propose a new Trojan horse attack, by which an eavesdropper Eve can gain full information about the key without being noticed, to real implementations of a counterfactual quantum cryptography system. Most importantly, the presented attack is available even if the system has negligible imperfections. Therefore, it shows that the present realization of counterfactual quantum key distribution is vulnerable.
Quantum walk public-key cryptographic system
NASA Astrophysics Data System (ADS)
Vlachou, C.; Rodrigues, J.; Mateus, P.; Paunković, N.; Souto, A.
2015-12-01
Quantum Cryptography is a rapidly developing field of research that benefits from the properties of Quantum Mechanics in performing cryptographic tasks. Quantum walks are a powerful model for quantum computation and very promising for quantum information processing. In this paper, we present a quantum public-key cryptographic system based on quantum walks. In particular, in the proposed protocol the public-key is given by a quantum state generated by performing a quantum walk. We show that the protocol is secure and analyze the complexity of public key generation and encryption/decryption procedures.
Dynamic visual cryptography based on chaotic oscillations
NASA Astrophysics Data System (ADS)
Petrauskiene, Vilma; Palivonaite, Rita; Aleksa, Algiment; Ragulskis, Minvydas
2014-01-01
Dynamic visual cryptography scheme based on chaotic oscillations is proposed in this paper. Special computational algorithms are required for hiding the secret image in the cover moiré grating, but the decryption of the secret is completely visual. The secret image is leaked in the form of time-averaged geometric moiré fringes when the cover image is oscillated by a chaotic law. The relationship among the standard deviation of the stochastic time variable, the pitch of the moiré grating and the pixel size ensuring visual decryption of the secret is derived. The parameters of these chaotic oscillations must be carefully preselected before the secret image is leaked from the cover image. Several computational experiments are used to illustrate the functionality and the applicability of the proposed image hiding technique.
NASA Astrophysics Data System (ADS)
Hwang, Tzonelih; Luo, Yi-Ping; Yang, Chun-Wei; Lin, Tzu-Han
2014-04-01
This work proposes a new direction in quantum cryptography called quantum authencryption. Quantum authencryption (QA), a new term to distinguish from authenticated quantum secure direct communications, is used to describe the technique of combining quantum encryption and quantum authentication into one process for off-line communicants. QA provides a new way of quantum communications without the presence of a receiver on line, and thus makes many applications depending on secure one-way quantum communications, such as quantum E-mail systems, possible. An example protocol using single photons and one-way hash functions is presented to realize the requirements on QA.
Towards secure quantum key distribution protocol for wireless LANs: a hybrid approach
NASA Astrophysics Data System (ADS)
Naik, R. Lalu; Reddy, P. Chenna
2015-12-01
The primary goals of security such as authentication, confidentiality, integrity and non-repudiation in communication networks can be achieved with secure key distribution. Quantum mechanisms are highly secure means of distributing secret keys as they are unconditionally secure. Quantum key distribution protocols can effectively prevent various attacks in the quantum channel, while classical cryptography is efficient in authentication and verification of secret keys. By combining both quantum cryptography and classical cryptography, security of communications over networks can be leveraged. Hwang, Lee and Li exploited the merits of both cryptographic paradigms for provably secure communications to prevent replay, man-in-the-middle, and passive attacks. In this paper, we propose a new scheme with the combination of quantum cryptography and classical cryptography for 802.11i wireless LANs. Since quantum cryptography is premature in wireless networks, our work is a significant step forward toward securing communications in wireless networks. Our scheme is known as hybrid quantum key distribution protocol. Our analytical results revealed that the proposed scheme is provably secure for wireless networks.
Quantum Image Encryption and Decryption Algorithms Based on Quantum Image Geometric Transformations
NASA Astrophysics Data System (ADS)
Zhou, Ri-Gui; Wu, Qian; Zhang, Man-Qun; Shen, Chen-Yi
2013-06-01
Cryptography is the essential subject for network information security to protect important data. Although following the symmetric cryptosystem for which the participations in the communication keep exactly the same keys, the special for the encryption and decryption algorithms proposed in this paper lays in the operational objectives, the quantum image. Firstly, extracts the properties of gray-scale and position from the quantum gray-scale image which the storage expression of image in quantum states is achieved. Along with the geometric transformations in classical images, this article realizes the quantum image geometric transforms by means of designing quantum circuits. Eventually, through a combination of the proposals in previous, the encryption and decryption algorithms on quantum gray-scale images is finally accomplished, which could ensure the confidentiality and security of the information in delivery. The algorithms belong to the application of quantum image geometric transformations, for further, the new explorations for quantum image cryptography researches.
Efficient Quantum Pseudorandomness
NASA Astrophysics Data System (ADS)
Brandão, Fernando G. S. L.; Harrow, Aram W.; Horodecki, Michał
2016-04-01
Randomness is both a useful way to model natural systems and a useful tool for engineered systems, e.g., in computation, communication, and control. Fully random transformations require exponential time for either classical or quantum systems, but in many cases pseudorandom operations can emulate certain properties of truly random ones. Indeed, in the classical realm there is by now a well-developed theory regarding such pseudorandom operations. However, the construction of such objects turns out to be much harder in the quantum case. Here, we show that random quantum unitary time evolutions ("circuits") are a powerful source of quantum pseudorandomness. This gives for the first time a polynomial-time construction of quantum unitary designs, which can replace fully random operations in most applications, and shows that generic quantum dynamics cannot be distinguished from truly random processes. We discuss applications of our result to quantum information science, cryptography, and understanding the self-equilibration of closed quantum dynamics.
Efficient Quantum Pseudorandomness.
Brandão, Fernando G S L; Harrow, Aram W; Horodecki, Michał
2016-04-29
Randomness is both a useful way to model natural systems and a useful tool for engineered systems, e.g., in computation, communication, and control. Fully random transformations require exponential time for either classical or quantum systems, but in many cases pseudorandom operations can emulate certain properties of truly random ones. Indeed, in the classical realm there is by now a well-developed theory regarding such pseudorandom operations. However, the construction of such objects turns out to be much harder in the quantum case. Here, we show that random quantum unitary time evolutions ("circuits") are a powerful source of quantum pseudorandomness. This gives for the first time a polynomial-time construction of quantum unitary designs, which can replace fully random operations in most applications, and shows that generic quantum dynamics cannot be distinguished from truly random processes. We discuss applications of our result to quantum information science, cryptography, and understanding the self-equilibration of closed quantum dynamics. PMID:27176509
Multilayer multicast key management with threshold cryptography
NASA Astrophysics Data System (ADS)
Dexter, Scott D.; Belostotskiy, Roman; Eskicioglu, Ahmet M.
2004-06-01
The problem of distributing multimedia securely over the Internet is often viewed as an instance of secure multicast communication, in which multicast messages are protected by a group key shared among the group of clients. One important class of key management schemes makes use of a hierarchical key distribution tree. Constructing a hierarchical tree based on secret shares rather than keys yields a scheme that is both more flexible and provably secure. Both the key-based and share-based hierarchical key distribution tree techniques are designed for managing keys for a single data stream. Recent work shows how redundancies that arise when this scheme is extended to multi-stream (e.g. scalable video) applications may be exploited in the key-based system by viewing the set of clients as a "multi-group". In this paper, we present results from an adaptation of a multi-group key management scheme using threshold cryptography. We describe how the multi-group scheme is adapted to work with secret shares, and compare this scheme with a naíve multi-stream key-management solution by measuring performance across several critical parameters, including tree degree, multi-group size, and number of shares stored at each node.
Optical scanning cryptography for secure wireless transmission
NASA Astrophysics Data System (ADS)
Poon, Ting-Chung; Kim, Taegeun; Doh, Kyu
2003-11-01
We propose a method for secure wireless transmission of encrypted information. By use of an encryption key, an image or document is optically encrypted by optical heterodyne scanning and hence encryption is performed on the fly. We call this technique optical scanning cryptography. The output of the heterodyne encrypted signal is at radio frequency and can be directly sent through an antenna to a secure site for digital storage to be prepared for decryption. In the secure site, an identical optical scanning system to that used for encryption is used, together with a decryption key, to generate an electrical signal. The electrical signal is then processed and sent to a computer to be used for decryption. Utilizing the stored information received from the encryption stage and the electrical information from the secure site, a digital decryption unit performs a decryption algorithm. If the encryption key and the decryption key are matched, the decryption unit will decrypt the image or document faithfully. The overall cryptosystem can perform the incoherent optical processing counterpart of the well-known coherent double-random phase-encoding technique. We present computer simulations of the idea.
Registration-tolerant extended visual cryptography
NASA Astrophysics Data System (ADS)
Nakajima, Mizuho; Yamaguchi, Yasushi
2003-06-01
Extended Visual Cryptography is a method which encodes a number of images so that when the images are superimposed, the hidden image appears without a trace of original images. The decryption is done directly by human eyes without cryptographic calculations. The proposing system takes three pictures as input and generates two images which correspond to two of the input pictures. The third picture is perceived by superimposing the two output images. Previous methods are based on halftoning and Boolean operations. Transparency values must be quantized before encryption, and a pixel is halftoned by a fixed numbers of completely transparent and opaque subpixels. Then a transparency of the superimposed pixel is controlled by changing the subpixel arrangements of the two output pixels. Since the subpixel arrangement is basically random, a tradeoff exists that to express the more graylevels, each subpixel must become the smaller, making it the more difficult to superimpose by hand. Our new approach tolerates registration error for the third image and eases the difficulty, by adopting concentric-circular subpixel arrangement and continuous grayscale subpixel values. The system becomes considerably robust to the registration error. Also, it achieves quality improvement for all three images, by explicitly dealing with continuous graylevels.
Optical scanning cryptography for secure wireless transmission.
Poon, Ting-Chung; Kim, Taegeun; Doh, Kyu
2003-11-10
We propose a method for secure wireless transmission of encrypted information. By use of an encryption key, an image or document is optically encrypted by optical heterodyne scanning and hence encryption is performed on the fly. We call this technique optical scanning cryptography. The output of the heterodyne encrypted signal is at radio frequency and can be directly sent through an antenna to a secure site for digital storage to be prepared for decryption. In the secure site, an identical optical scanning system to that used for encryption is used, together with a decryption key, to generate an electrical signal. The electrical signal is then processed and sent to a computer to be used for decryption. Utilizing the stored information received from the encryption stage and the electrical information from the secure site, a digital decryption unit performs a decryption algorithm. If the encryption key and the decryption key are matched, the decryption unit will decrypt the image or document faithfully. The overall cryptosystem can perform the incoherent optical processing counterpart of the well-known coherent double-random phase-encoding technique. We present computer simulations of the idea. PMID:14650492
Secure communications with low-orbit spacecraft using quantum cryptography
Hughes, Richard J.; Buttler, William T.; Kwiat, Paul G.; Luther, Gabriel G.; Morgan, George L; Nordholt, Jane E.; Peterson, Charles G.; Simmons, Charles M.
1999-01-01
Apparatus and method for secure communication between an earth station and spacecraft. A laser outputs single pulses that are split into preceding bright pulses and delayed attenuated pulses, and polarized. A Pockels cell changes the polarization of the polarized delayed attenuated pulses according to a string of random numbers, a first polarization representing a "1," and a second polarization representing a "0." At the receiving station, a beamsplitter randomly directs the preceding bright pulses and the polarized delayed attenuated pulses onto longer and shorter paths, both terminating in a beamsplitter which directs the preceding bright pulses and a first portion of the polarized delayed attenuated pulses to a first detector, and a second portion of the polarized delayed attenuated pulses to a second detector to generate a key for secure communication between the earth station and the spacecraft.
Optical visual cryptography based on the phase characteristics of spatial light modulator
NASA Astrophysics Data System (ADS)
Yi, Sang-Yi; Ryu, Chung-Sang; Lee, Seung-Hyun
2006-09-01
Optical visual cryptography based on binary computer generated hologram (BCGH) was proposed which used optics instead of human eyesight for decryption. As a result, it was possible to adapt cryptography to optical system. However, it also had some difficulties because it did not overcome the existing problem of visual cryptography completely. This paper suggested the method of optical cryptography implementation based on the phase modulation characteristics of liquid crystal display (LCD). The problems and appropriations are evaluated with some simulation. This system showed that the noise was reduced and resolution was improved compare with the conventional optical visual cryptography.
Implementation of Elliptic Curve Cryptography in Binary Field
NASA Astrophysics Data System (ADS)
Susantio, D. R.; Muchtadi-Alamsyah, I.
2016-04-01
Currently, there is a steadily increasing demand of information security, caused by a surge in information flow. There are many ways to create a secure information channel, one of which is to use cryptography. In this paper, we discuss the implementation of elliptic curves over the binary field for cryptography. We use the simplified version of the ECIES (Elliptic Curve Integrated Encryption Scheme). The ECIES encrypts a plaintext by masking the original message using specified points on the curve. The encryption process is done by separating the plaintext into blocks. Each block is then separately encrypted using the encryption scheme.
A halftone visual cryptography schema using ordered dither
NASA Astrophysics Data System (ADS)
Feng, Liu-Ping; Cong, Dong-Sheng; Liu, Hua-Qun; Wang, Meng-Min
2014-04-01
Visual cryptography is a cryptographic technique which allows visual information to be encrypted in such a way that the decryption can be performed by the human visual system, without the aid of computers. This paper proposes a schema of information hiding within the method of visual cryptography. The gray image is changed into two halftone images via the different dither matrixes respectively, and the secret binary pixels are encoded into shares. The secret information can be restored by stacking the different shared halftone images together. Simulation results show that the secret binary image can be decoded efficiently.
Visual cryptography based on optical interference encryption technique
NASA Astrophysics Data System (ADS)
Seo, Dong-Hoan; Kim, Jong-Yun; Lee, Sang-Su; Park, Se-Joon; Cho, Woong H.; Kim, Soo-Joong
2001-07-01
In this paper, we proposed a new visual cryptography scheme based on optical interference that can improve the contrast and signal to noise ratio of reconstructed images when compared to conventional visual cryptography methods. The binary image being encrypted is divided into any number of n slides. For encryption, randomly independent keys are generated along with another random key based on a XOR process of random keys. The XOR process between each divided image and each random key produces the encryption of n encrypted images. These encrypted images are then used to make encrypted binary phase masks. For decryption, the phase masks are placed on the paths of a Mach-Zehnder interferometer.
Securing resource constraints embedded devices using elliptic curve cryptography
NASA Astrophysics Data System (ADS)
Tam, Tony; Alfasi, Mohamed; Mozumdar, Mohammad
2014-06-01
The use of smart embedded device has been growing rapidly in recent time because of miniaturization of sensors and platforms. Securing data from these embedded devices is now become one of the core challenges both in industry and research community. Being embedded, these devices have tight constraints on resources such as power, computation, memory, etc. Hence it is very difficult to implement traditional Public Key Cryptography (PKC) into these resource constrained embedded devices. Moreover, most of the public key security protocols requires both public and private key to be generated together. In contrast with this, Identity Based Encryption (IBE), a public key cryptography protocol, allows a public key to be generated from an arbitrary string and the corresponding private key to be generated later on demand. While IBE has been actively studied and widely applied in cryptography research, conventional IBE primitives are also computationally demanding and cannot be efficiently implemented on embedded system. Simplified version of the identity based encryption has proven its competence in being robust and also satisfies tight budget of the embedded platform. In this paper, we describe the choice of several parameters for implementing lightweight IBE in resource constrained embedded sensor nodes. Our implementation of IBE is built using elliptic curve cryptography (ECC).
Enhancing Undergraduate Mathematics Curriculum via Coding Theory and Cryptography
ERIC Educational Resources Information Center
Aydin, Nuh
2009-01-01
The theory of error-correcting codes and cryptography are two relatively recent applications of mathematics to information and communication systems. The mathematical tools used in these fields generally come from algebra, elementary number theory, and combinatorics, including concepts from computational complexity. It is possible to introduce the…
Information Divergence and Distance Measures for Quantum States
NASA Astrophysics Data System (ADS)
Jiang, Nan; Zhang, Zhaozhi
2015-02-01
Both information divergence and distance are measures of closeness of two quantum states which are widely used in the theory of information processing and quantum cryptography. For example, the quantum relative entropy and trace distance are well known. Here we introduce a number of new quantum information divergence and distance measures into the literature and discuss their relations and properties. We also propose a method to analyze the properties and relations of various distance and pseudo-distance measures.
Trojan horse attacks on counterfactual quantum key distribution
NASA Astrophysics Data System (ADS)
Yang, Xiuqing; Wei, Kejin; Ma, Haiqiang; Sun, Shihai; Du, Yungang; Wu, Lingan
2016-04-01
There has been much interest in "counterfactual quantum cryptography" (T.-G. Noh, 2009 [10]). It seems that the counterfactual quantum key distribution protocol without any photon carrier through the quantum channel provides practical security advantages. However, we show that it is easy to break counterfactual quantum key distribution systems in practical situations. We introduce the two types of Trojan horse attacks that are available for the two-way protocol and become possible for practical counterfactual systems with our eavesdropping schemes.
NASA Astrophysics Data System (ADS)
Le Gouët, Jean-Louis; Moiseev, Sergey
2012-06-01
quest for higher efficiency, better fidelity, broader bandwidth, multimode capacity and longer storage lifetime is pursued in all those approaches, as shown in this special issue. The improvement of quantum memory operation specifically requires in-depth study and control of numerous physical processes leading to atomic decoherence. The present issue reflects the development of rare earth ion doped matrices offering long lifetime superposition states, either as bulk crystals or as optical waveguides. The need for quantum sources and high efficiency detectors at the single photon level is also illustrated. Several papers address the networking of quantum memories either in long-haul cryptography or in the prospect of quantum processing. In this context, much attention has been paid recently to interfacing quantum light with superconducting qubits and with nitrogen-vacancy centers in diamond. Finally, the quantum interfacing of light with matter raises questions on entanglement. The last two papers are devoted to the generation of entanglement by dissipative processes. It is shown that long lifetime entanglement may be built in this way. We hope this special issue will help readers to become familiar with the exciting field of ensemble-based quantum memories and will stimulate them to bring deeper insights and new ideas to this area.
Counterfactual quantum certificate authorization
NASA Astrophysics Data System (ADS)
Shenoy H., Akshata; Srikanth, R.; Srinivas, T.
2014-05-01
We present a multipartite protocol in a counterfactual paradigm. In counterfactual quantum cryptography, secure information is transmitted between two spatially separated parties even when there is no physical travel of particles transferring the information between them. We propose here a tripartite counterfactual quantum protocol for the task of certificate authorization. Here a trusted third party, Alice, authenticates an entity Bob (e.g., a bank) that a client Charlie wishes to securely transact with. The protocol is counterfactual with respect to either Bob or Charlie. We prove its security against a general incoherent attack, where Eve attacks single particles.
Two New Chaotic Cryptographies Based on Different Attractor-Partition Algorithms
NASA Astrophysics Data System (ADS)
Wang, Xingyuan; Liu, Ming; Gu, Nini
The paper analyses the limitation of Baptista cryptography in partitioning an attractor, and proposes two new attractor-partition methods: uniform-partition algorithm and dynamic-partition algorithm. They are different from the equal-interval-partition algorithm in Baptista cryptography, but dividing the attractor according to the attractor's natural invariant density and plaintext density, respectively. The comparative experiment indicates: the two new methods improve the unbalanced cryptograph distribution and cryptograph length in Baptista cryptography, they are also able to reduce the iteration time in chaotic systems effectively, which has improved decryption time and cryptographies' security.
Electronic Voting Protocol Using Identity-Based Cryptography.
Gallegos-Garcia, Gina; Tapia-Recillas, Horacio
2015-01-01
Electronic voting protocols proposed to date meet their properties based on Public Key Cryptography (PKC), which offers high flexibility through key agreement protocols and authentication mechanisms. However, when PKC is used, it is necessary to implement Certification Authority (CA) to provide certificates which bind public keys to entities and enable verification of such public key bindings. Consequently, the components of the protocol increase notably. An alternative is to use Identity-Based Encryption (IBE). With this kind of cryptography, it is possible to have all the benefits offered by PKC, without neither the need of certificates nor all the core components of a Public Key Infrastructure (PKI). Considering the aforementioned, in this paper we propose an electronic voting protocol, which meets the privacy and robustness properties by using bilinear maps. PMID:26090515
Electronic Voting Protocol Using Identity-Based Cryptography
Gallegos-Garcia, Gina; Tapia-Recillas, Horacio
2015-01-01
Electronic voting protocols proposed to date meet their properties based on Public Key Cryptography (PKC), which offers high flexibility through key agreement protocols and authentication mechanisms. However, when PKC is used, it is necessary to implement Certification Authority (CA) to provide certificates which bind public keys to entities and enable verification of such public key bindings. Consequently, the components of the protocol increase notably. An alternative is to use Identity-Based Encryption (IBE). With this kind of cryptography, it is possible to have all the benefits offered by PKC, without neither the need of certificates nor all the core components of a Public Key Infrastructure (PKI). Considering the aforementioned, in this paper we propose an electronic voting protocol, which meets the privacy and robustness properties by using bilinear maps. PMID:26090515
Digital Cryptography and Feedback Synchronization of Chaotic Systems
NASA Astrophysics Data System (ADS)
Mitra, Mala; Banerjee, Santo
Secure communications via chaotic synchronization is demonstrated in this literature. At first we have designed a feedback controller for chaotic synchronization utilizing the Lyapunov stability theory for cascade-connected systems.The method has been applied successfully to make two identical systems globally asymptotically synchronized. The result of numerical simulations are given to validate the effectiveness of this method. Then we have discussed a new method of cryptography for this coupled system which is very simple to implement and effective.
Quantum random number generation
Ma, Xiongfeng; Yuan, Xiao; Cao, Zhu; Zhang, Zhen; Qi, Bing
2016-01-01
Here, quantum physics can be exploited to generate true random numbers, which play important roles in many applications, especially in cryptography. Genuine randomness from the measurement of a quantum system reveals the inherent nature of quantumness — coherence, an important feature that differentiates quantum mechanics from classical physics. The generation of genuine randomness is generally considered impossible with only classical means. Based on the degree of trustworthiness on devices, quantum random number generators (QRNGs) can be grouped into three categories. The first category, practical QRNG, is built on fully trusted and calibrated devices and typically can generate randomness at a high speed by properly modeling the devices. The second category is self-testing QRNG, where verifiable randomness can be generated without trusting the actual implementation. The third category, semi-self-testing QRNG, is an intermediate category which provides a tradeoff between the trustworthiness on the device and the random number generation speed.
Practical quantum retrieval games
NASA Astrophysics Data System (ADS)
Arrazola, Juan Miguel; Karasamanis, Markos; Lütkenhaus, Norbert
2016-06-01
Complex cryptographic protocols are often constructed from simpler building blocks. In order to advance quantum cryptography, it is important to study practical building blocks that can be used to develop new protocols. An example is quantum retrieval games (QRGs), which have broad applicability and have already been used to construct quantum money schemes. In this work, we introduce a general construction of quantum retrieval games based on the hidden matching problem and show how they can be implemented in practice using available technology. More precisely, we provide a general method to construct (1-out-of-k ) QRGs, proving that their cheating probabilities decrease exponentially in k . In particular, we define QRGs based on coherent states of light, which can be implemented even in the presence of experimental imperfections. Our results constitute a tool in the arsenal of the practical quantum cryptographer.
Quantum random number generation
Ma, Xiongfeng; Yuan, Xiao; Cao, Zhu; Zhang, Zhen; Qi, Bing
2016-06-28
Here, quantum physics can be exploited to generate true random numbers, which play important roles in many applications, especially in cryptography. Genuine randomness from the measurement of a quantum system reveals the inherent nature of quantumness -- coherence, an important feature that differentiates quantum mechanics from classical physics. The generation of genuine randomness is generally considered impossible with only classical means. Based on the degree of trustworthiness on devices, quantum random number generators (QRNGs) can be grouped into three categories. The first category, practical QRNG, is built on fully trusted and calibrated devices and typically can generate randomness at amore » high speed by properly modeling the devices. The second category is self-testing QRNG, where verifiable randomness can be generated without trusting the actual implementation. The third category, semi-self-testing QRNG, is an intermediate category which provides a tradeoff between the trustworthiness on the device and the random number generation speed.« less
Fast, Parallel and Secure Cryptography Algorithm Using Lorenz's Attractor
NASA Astrophysics Data System (ADS)
Marco, Anderson Gonçalves; Martinez, Alexandre Souto; Bruno, Odemir Martinez
A novel cryptography method based on the Lorenz's attractor chaotic system is presented. The proposed algorithm is secure and fast, making it practical for general use. We introduce the chaotic operation mode, which provides an interaction among the password, message and a chaotic system. It ensures that the algorithm yields a secure codification, even if the nature of the chaotic system is known. The algorithm has been implemented in two versions: one sequential and slow and the other, parallel and fast. Our algorithm assures the integrity of the ciphertext (we know if it has been altered, which is not assured by traditional algorithms) and consequently its authenticity. Numerical experiments are presented, discussed and show the behavior of the method in terms of security and performance. The fast version of the algorithm has a performance comparable to AES, a popular cryptography program used commercially nowadays, but it is more secure, which makes it immediately suitable for general purpose cryptography applications. An internet page has been set up, which enables the readers to test the algorithm and also to try to break into the cipher.
Measurement-device-independent quantum key distribution.
Lo, Hoi-Kwong; Curty, Marcos; Qi, Bing
2012-03-30
How to remove detector side channel attacks has been a notoriously hard problem in quantum cryptography. Here, we propose a simple solution to this problem--measurement-device-independent quantum key distribution (QKD). It not only removes all detector side channels, but also doubles the secure distance with conventional lasers. Our proposal can be implemented with standard optical components with low detection efficiency and highly lossy channels. In contrast to the previous solution of full device independent QKD, the realization of our idea does not require detectors of near unity detection efficiency in combination with a qubit amplifier (based on teleportation) or a quantum nondemolition measurement of the number of photons in a pulse. Furthermore, its key generation rate is many orders of magnitude higher than that based on full device independent QKD. The results show that long-distance quantum cryptography over say 200 km will remain secure even with seriously flawed detectors. PMID:22540686
A library for prototyping the computer arithmetic level in elliptic curve cryptography
NASA Astrophysics Data System (ADS)
Imbert, Laurent; Peirera, Agostinho; Tisserand, Arnaud
2007-09-01
This paper presents the first version of a software library called PACE ("Prototyping Arithmetic in Cryptography Easily"). This is a C++ library under LGPL license. It provides number systems and algorithms for prototyping the arithmetic layer in cryptographic applications. The first version of PACE includes basic support of prime finite fields and ECC (Elliptic Curve Cryptography) basic algorithms for software implementations.
Fully Distrustful Quantum Bit Commitment and Coin Flipping
NASA Astrophysics Data System (ADS)
Silman, J.; Chailloux, A.; Aharon, N.; Kerenidis, I.; Pironio, S.; Massar, S.
2011-06-01
In the distrustful quantum cryptography model the parties have conflicting interests and do not trust one another. Nevertheless, they trust the quantum devices in their labs. The aim of the device-independent approach to cryptography is to do away with the latter assumption, and, consequently, significantly increase security. It is an open question whether the scope of this approach also extends to protocols in the distrustful cryptography model, thereby rendering them “fully” distrustful. In this Letter, we show that for bit commitment—one of the most basic primitives within the model—the answer is positive. We present a device-independent (imperfect) bit-commitment protocol, where Alice’s and Bob’s cheating probabilities are ≃0.854 and (3)/(4), which we then use to construct a device-independent coin flipping protocol with bias ≲0.336.
Remapping the quantum frontier
NASA Astrophysics Data System (ADS)
Monroe, Christopher; Lukin, Mikhail
2008-08-01
In 1994 the mathematician Peter Shor, then working at AT&T Bell Laboratories in the US, applied quantum mechanics to an age-old problem in number theory and made a remarkable discovery. He showed that a computer that operates on and processes quantum systems could factor large integers exponentially faster than a conventional computer. This result attracted a lot of attention because the difficulty of factoring large numbers is what ensures the security of modern cryptography schemes - even the best conventional computer would take several thousand years to factor a number with more than about 150 digits. Shor's quantum factoring algorithm could, in principle, break such encryption standards - a possibility that led to an explosion of interest in quantum information science. Until then it was a field that had largely been a mere curiosity, despite notable contributions from the likes of Richard Feynman and David Deutsch.
An application of different dioids in public key cryptography
Durcheva, Mariana I.
2014-11-18
Dioids provide a natural framework for analyzing a broad class of discrete event dynamical systems such as the design and analysis of bus and railway timetables, scheduling of high-throughput industrial processes, solution of combinatorial optimization problems, the analysis and improvement of flow systems in communication networks. They have appeared in several branches of mathematics such as functional analysis, optimization, stochastic systems and dynamic programming, tropical geometry, fuzzy logic. In this paper we show how to involve dioids in public key cryptography. The main goal is to create key – exchange protocols based on dioids. Additionally the digital signature scheme is presented.
Novel optical scanning cryptography using Fresnel telescope imaging.
Yan, Aimin; Sun, Jianfeng; Hu, Zhijuan; Zhang, Jingtao; Liu, Liren
2015-07-13
We propose a new method called modified optical scanning cryptography using Fresnel telescope imaging technique for encryption and decryption of remote objects. An image or object can be optically encrypted on the fly by Fresnel telescope scanning system together with an encryption key. For image decryption, the encrypted signals are received and processed with an optical coherent heterodyne detection system. The proposed method has strong performance through use of secure Fresnel telescope scanning with orthogonal polarized beams and efficient all-optical information processing. The validity of the proposed method is demonstrated by numerical simulations and experimental results. PMID:26191901
Fourier-based automatic alignment for improved Visual Cryptography schemes.
Machizaud, Jacques; Chavel, Pierre; Fournel, Thierry
2011-11-01
In Visual Cryptography, several images, called "shadow images", that separately contain no information, are overlapped to reveal a shared secret message. We develop a method to digitally register one printed shadow image acquired by a camera with a purely digital shadow image, stored in memory. Using Fourier techniques derived from Fourier Optics concepts, the idea is to enhance and exploit the quasi periodicity of the shadow images, composed by a random distribution of black and white patterns on a periodic sampling grid. The advantage is to speed up the security control or the access time to the message, in particular in the cases of a small pixel size or of large numbers of pixels. Furthermore, the interest of visual cryptography can be increased by embedding the initial message in two shadow images that do not have identical mathematical supports, making manual registration impractical. Experimental results demonstrate the successful operation of the method, including the possibility to directly project the result onto the printed shadow image. PMID:22109152
Secure satellite communication using multi-photon tolerant quantum communication protocol
NASA Astrophysics Data System (ADS)
Darunkar, Bhagyashri; Punekar, Nikhil; Verma, Pramode K.
2015-09-01
This paper proposes and analyzes the potential of a multi-photon tolerant quantum communication protocol to secure satellite communication. For securing satellite communication, quantum cryptography is the only known unconditionally secure method. A number of recent experiments have shown feasibility of satellite-aided global quantum key distribution (QKD) using different methods such as: Use of entangled photon pairs, decoy state methods, and entanglement swapping. The use of single photon in these methods restricts the distance and speed over which quantum cryptography can be applied. Contemporary quantum cryptography protocols like the BB84 and its variants suffer from the limitation of reaching the distances of only Low Earth Orbit (LEO) at the data rates of few kilobits per second. This makes it impossible to develop a general satellite-based secure global communication network using the existing protocols. The method proposed in this paper allows secure communication at the heights of the Medium Earth Orbit (MEO) and Geosynchronous Earth Orbit (GEO) satellites. The benefits of the proposed method are two-fold: First it enables the realization of a secure global communication network based on satellites and second it provides unconditional security for satellite networks at GEO heights. The multi-photon approach discussed in this paper ameliorates the distance and speed issues associated with quantum cryptography through the use of contemporary laser communication (lasercom) devices. This approach can be seen as a step ahead towards global quantum communication.
Quantum Oblivious Transfer Based on a Quantum Symmetrically Private Information Retrieval Protocol
NASA Astrophysics Data System (ADS)
Yang, Yu-Guang; Sun, Si-Jia; Wang, Yan
2015-03-01
Private information retrieval implies oblivious transfer in classical cryptography. Following this clue, we present a novel quantum one-out-of-two OT protocol based on a practical quantum symmetrically private information retrieval protocol Jakobi et al. (Phys. Rev. A 83, 022301 2011), with changes only in the classical postprocessing of the key. While unconditionally secure oblivious transfer is known to be impossible, we argue that an interesting degree of security can be achieved by means of quantum physical principles instead of unproven security assumptions in order to protect both the sender and the receiver. The proposed OT protocol is loss tolerant, practical and robust against quantum memory attack.
Quantum proxy signature scheme with public verifiability
NASA Astrophysics Data System (ADS)
Zhou, Jingxian; Zhou, Yajian; Niu, Xinxin; Yang, Yixian
2011-10-01
In recent years, with the development of quantum cryptography, quantum signature has also made great achievement. However, the effectiveness of all the quantum signature schemes reported in the literature can only be verified by a designated person. Therefore, its wide applications are limited. For solving this problem, a new quantum proxy signature scheme using EPR quantum entanglement state and unitary transformation to generate proxy signature is presented. Proxy signer announces his public key when he generates the final signature. According to the property of unitary transformation and quantum one-way function, everyone can verify whether the signature is effective or not by the public key. So the quantum proxy signature scheme in our paper can be public verified. The quantum key distribution and one-time pad encryption algorithm guarantee the unconditional security of this scheme. Analysis results show that this new scheme satisfies strong non-counterfeit and strong non-disavowal.
Reliable Freestanding Position-Based Routing in Highway Scenarios
Galaviz-Mosqueda, Gabriel A.; Aquino-Santos, Raúl; Villarreal-Reyes, Salvador; Rivera-Rodríguez, Raúl; Villaseñor-González, Luis; Edwards, Arthur
2012-01-01
Vehicular Ad Hoc Networks (VANETs) are considered by car manufacturers and the research community as the enabling technology to radically improve the safety, efficiency and comfort of everyday driving. However, before VANET technology can fulfill all its expected potential, several difficulties must be addressed. One key issue arising when working with VANETs is the complexity of the networking protocols compared to those used by traditional infrastructure networks. Therefore, proper design of the routing strategy becomes a main issue for the effective deployment of VANETs. In this paper, a reliable freestanding position-based routing algorithm (FPBR) for highway scenarios is proposed. For this scenario, several important issues such as the high mobility of vehicles and the propagation conditions may affect the performance of the routing strategy. These constraints have only been partially addressed in previous proposals. In contrast, the design approach used for developing FPBR considered the constraints imposed by a highway scenario and implements mechanisms to overcome them. FPBR performance is compared to one of the leading protocols for highway scenarios. Performance metrics show that FPBR yields similar results when considering freespace propagation conditions, and outperforms the leading protocol when considering a realistic highway path loss model. PMID:23202159
Reliable freestanding position-based routing in highway scenarios.
Galaviz-Mosqueda, Gabriel A; Aquino-Santos, Raúl; Villarreal-Reyes, Salvador; Rivera-Rodríguez, Raúl; Villaseñor-González, Luis; Edwards, Arthur
2012-01-01
Vehicular Ad Hoc Networks (VANETs) are considered by car manufacturers and the research community as the enabling technology to radically improve the safety, efficiency and comfort of everyday driving. However, before VANET technology can fulfill all its expected potential, several difficulties must be addressed. One key issue arising when working with VANETs is the complexity of the networking protocols compared to those used by traditional infrastructure networks. Therefore, proper design of the routing strategy becomes a main issue for the effective deployment of VANETs. In this paper, a reliable freestanding position-based routing algorithm (FPBR) for highway scenarios is proposed. For this scenario, several important issues such as the high mobility of vehicles and the propagation conditions may affect the performance of the routing strategy. These constraints have only been partially addressed in previous proposals. In contrast, the design approach used for developing FPBR considered the constraints imposed by a highway scenario and implements mechanisms to overcome them. FPBR performance is compared to one of the leading protocols for highway scenarios. Performance metrics show that FPBR yields similar results when considering freespace propagation conditions, and outperforms the leading protocol when considering a realistic highway path loss model. PMID:23202159
Implementing Diffie-Hellman key exchange using quantum EPR pairs
NASA Astrophysics Data System (ADS)
Mandal, Sayonnha; Parakh, Abhishek
2015-05-01
This paper implements the concepts of perfect forward secrecy and the Diffie-Hellman key exchange using EPR pairs to establish and share a secret key between two non-authenticated parties and transfer messages between them without the risk of compromise. Current implementations of quantum cryptography are based on the BB84 protocol, which is susceptible to siphoning attacks on the multiple photons emitted by practical laser sources. This makes BB84-based quantum cryptography protocol unsuitable for network computing environments. Diffie-Hellman does not require the two parties to be mutually authenticated to each other, yet it can provide a basis for a number of authenticated protocols, most notably the concept of perfect forward secrecy. The work proposed in this paper provides a new direction in utilizing quantum EPR pairs in quantum key exchange. Although, classical cryptography boasts of efficient and robust protocols like the Diffie-Hellman key exchange, in the current times, with the advent of quantum computing they are very much vulnerable to eavesdropping and cryptanalytic attacks. Using quantum cryptographic principles, however, these classical encryption algorithms show more promise and a more robust and secure structure for applications. The unique properties of quantum EPR pairs also, on the other hand, go a long way in removing attacks like eavesdropping by their inherent nature of one particle of the pair losing its state if a measurement occurs on the other. The concept of perfect forward secrecy is revisited in this paper to attribute tighter security to the proposed protocol.
Image communication scheme based on dynamic visual cryptography and computer generated holography
NASA Astrophysics Data System (ADS)
Palevicius, Paulius; Ragulskis, Minvydas
2015-01-01
Computer generated holograms are often exploited to implement optical encryption schemes. This paper proposes the integration of dynamic visual cryptography (an optical technique based on the interplay of visual cryptography and time-averaging geometric moiré) with Gerchberg-Saxton algorithm. A stochastic moiré grating is used to embed the secret into a single cover image. The secret can be visually decoded by a naked eye if only the amplitude of harmonic oscillations corresponds to an accurately preselected value. The proposed visual image encryption scheme is based on computer generated holography, optical time-averaging moiré and principles of dynamic visual cryptography. Dynamic visual cryptography is used both for the initial encryption of the secret image and for the final decryption. Phase data of the encrypted image are computed by using Gerchberg-Saxton algorithm. The optical image is decrypted using the computationally reconstructed field of amplitudes.
Cryptanalysis and security enhancement of optical cryptography based on computational ghost imaging
NASA Astrophysics Data System (ADS)
Yuan, Sheng; Yao, Jianbin; Liu, Xuemei; Zhou, Xin; Li, Zhongyang
2016-04-01
Optical cryptography based on computational ghost imaging (CGI) has attracted much attention of researchers because it encrypts plaintext into a random intensity vector rather than complexed-valued function. This promising feature of the CGI-based cryptography reduces the amount of data to be transmitted and stored and therefore brings convenience in practice. However, we find that this cryptography is vulnerable to chosen-plaintext attack because of the linear relationship between the input and output of the encryption system, and three feasible strategies are proposed to break it in this paper. Even though a large number of plaintexts need to be chosen in these attack methods, it means that this cryptography still exists security risks. To avoid these attacks, a security enhancement method utilizing an invertible matrix modulation is further discussed and the feasibility is verified by numerical simulations.
Novel Quantum Proxy Signature without Entanglement
NASA Astrophysics Data System (ADS)
Xu, Guang-bao
2015-08-01
Proxy signature is an important research topic in classic cryptography since it has many application occasions in our real life. But only a few quantum proxy signature schemes have been proposed up to now. In this paper, we propose a quantum proxy signature scheme, which is designed based on quantum one-time pad. Our scheme can be realized easily since it only uses single-particle states. Security analysis shows that it is secure and meets all the properties of a proxy signature, such as verifiability, distinguishability, unforgeability and undeniability.
Quantum Information with Structured Light
NASA Astrophysics Data System (ADS)
Mirhosseini, Mohammad
Quantum information science promises dramatic progress in a variety of fields such as cryptography, computation, and metrology. Although the proof-of-principle attempts for implementing quantum protocols have often relied on only a few qubits, the utilization of more sophisticated quantum systems is required for practical applications. In this thesis, we investigate the emerging role of high-dimensional optical states as a resource for encoding quantum information. We begin the first chapter with a review of orbital angular momentum (OAM) as a prime candidate for realizing multilevel quantum states and follow with a brief introduction to the quantum measurement theory. The second and the third chapters are dedicated to the application of OAM modes in quantum cryptography. In the second chapter, we discuss the challenges of projective measurement of OAM at the single-photon level, a crucial task required for quantum information processing. We then present our development of an efficient and accurate mode-sorting device that is capable of projectively measuring the orbital angular momentum of single photons. In the third chapter, we discuss the role of OAM modes in increasing the information capacity of quantum cryptography. We start this chapter by establishing the merits of encoding information on the quantum index of OAM modes in a free-space link. We then generalizing the BB-84 QKD protocol to the Hilbert space spanned by a finite number of OAM modes and outline our experimental realization. The last two chapters are dedicated to the tomography of structured light fields. We start the fourth chapter by applying the recently found method of direct measurement to the characterization of OAM superpositions. We find the quantum state in the Hilbert space spanned by 27 OAM modes by performing a weak measurement of orbital angular momentum (OAM) followed by a strong measurement of azimuthal angle. We then introduce the concept of compressive direct measurement (CDM
Optimal architectures for long distance quantum communication
Muralidharan, Sreraman; Li, Linshu; Kim, Jungsang; Lütkenhaus, Norbert; Lukin, Mikhail D.; Jiang, Liang
2016-01-01
Despite the tremendous progress of quantum cryptography, efficient quantum communication over long distances (≥1000 km) remains an outstanding challenge due to fiber attenuation and operation errors accumulated over the entire communication distance. Quantum repeaters (QRs), as a promising approach, can overcome both photon loss and operation errors, and hence significantly speedup the communication rate. Depending on the methods used to correct loss and operation errors, all the proposed QR schemes can be classified into three categories (generations). Here we present the first systematic comparison of three generations of quantum repeaters by evaluating the cost of both temporal and physical resources, and identify the optimized quantum repeater architecture for a given set of experimental parameters for use in quantum key distribution. Our work provides a roadmap for the experimental realizations of highly efficient quantum networks over transcontinental distances. PMID:26876670
Prospects for quantum computation with trapped ions
Hughes, R.J.; James, D.F.V.
1997-12-31
Over the past decade information theory has been generalized to allow binary data to be represented by two-state quantum mechanical systems. (A single two-level system has come to be known as a qubit in this context.) The additional freedom introduced into information physics with quantum systems has opened up a variety of capabilities that go well beyond those of conventional information. For example, quantum cryptography allows two parties to generate a secret key even in the presence of eavesdropping. But perhaps the most remarkable capabilities have been predicted in the field of quantum computation. Here, a brief survey of the requirements for quantum computational hardware, and an overview of the in trap quantum computation project at Los Alamos are presented. The physical limitations to quantum computation with trapped ions are discussed.
Optimal architectures for long distance quantum communication.
Muralidharan, Sreraman; Li, Linshu; Kim, Jungsang; Lütkenhaus, Norbert; Lukin, Mikhail D; Jiang, Liang
2016-01-01
Despite the tremendous progress of quantum cryptography, efficient quantum communication over long distances (≥ 1000 km) remains an outstanding challenge due to fiber attenuation and operation errors accumulated over the entire communication distance. Quantum repeaters (QRs), as a promising approach, can overcome both photon loss and operation errors, and hence significantly speedup the communication rate. Depending on the methods used to correct loss and operation errors, all the proposed QR schemes can be classified into three categories (generations). Here we present the first systematic comparison of three generations of quantum repeaters by evaluating the cost of both temporal and physical resources, and identify the optimized quantum repeater architecture for a given set of experimental parameters for use in quantum key distribution. Our work provides a roadmap for the experimental realizations of highly efficient quantum networks over transcontinental distances. PMID:26876670
Authentication Protocol using Quantum Superposition States
Kanamori, Yoshito; Yoo, Seong-Moo; Gregory, Don A.; Sheldon, Frederick T
2009-01-01
When it became known that quantum computers could break the RSA (named for its creators - Rivest, Shamir, and Adleman) encryption algorithm within a polynomial-time, quantum cryptography began to be actively studied. Other classical cryptographic algorithms are only secure when malicious users do not have sufficient computational power to break security within a practical amount of time. Recently, many quantum authentication protocols sharing quantum entangled particles between communicators have been proposed, providing unconditional security. An issue caused by sharing quantum entangled particles is that it may not be simple to apply these protocols to authenticate a specific user in a group of many users. An authentication protocol using quantum superposition states instead of quantum entangled particles is proposed. The random number shared between a sender and a receiver can be used for classical encryption after the authentication has succeeded. The proposed protocol can be implemented with the current technologies we introduce in this paper.
Optimal architectures for long distance quantum communication
NASA Astrophysics Data System (ADS)
Muralidharan, Sreraman; Li, Linshu; Kim, Jungsang; Lütkenhaus, Norbert; Lukin, Mikhail D.; Jiang, Liang
2016-02-01
Despite the tremendous progress of quantum cryptography, efficient quantum communication over long distances (≥1000 km) remains an outstanding challenge due to fiber attenuation and operation errors accumulated over the entire communication distance. Quantum repeaters (QRs), as a promising approach, can overcome both photon loss and operation errors, and hence significantly speedup the communication rate. Depending on the methods used to correct loss and operation errors, all the proposed QR schemes can be classified into three categories (generations). Here we present the first systematic comparison of three generations of quantum repeaters by evaluating the cost of both temporal and physical resources, and identify the optimized quantum repeater architecture for a given set of experimental parameters for use in quantum key distribution. Our work provides a roadmap for the experimental realizations of highly efficient quantum networks over transcontinental distances.
Security of quantum key distribution with entangled qutrits
Durt, Thomas; Cerf, Nicolas J.; Gisin, Nicolas; Zukowski, Marek
2003-01-01
The study of quantum cryptography and quantum entanglement have traditionally been based on two-level quantum systems (qubits). In this paper, we consider a generalization of Ekert's entanglement-based quantum cryptographic protocol where qubits are replaced by three-level systems (qutrits). In order to investigate the security against the optimal individual attack, we derive the information gained by a potential eavesdropper applying a cloning-based attack. We exhibit the explicit form of this cloner, which is distinct from the previously known cloners, and conclude that the protocol is more robust than those based on entangled qubits as well as unentangled qutrits.
A public-key cryptosystem for quantum message transmission
NASA Astrophysics Data System (ADS)
Yang, Li
2005-01-01
We present a quantum public-key cryptography protocol for quantum message transmission. The private key of this protocol includes three classical matrices: a generator matrix of a Goppa code, an invertible matrix and a permutation matrix. The public key is product of these three matrices. The encryption and decryption algorithms are merely quantum computations related with the transformations between bases of the quantum registers. The security of this protocol is based on the hypothesis that there is no effective algorithm of NP-complete problem.
Secure self-calibrating quantum random-bit generator
Fiorentino, M.; Santori, C.; Spillane, S. M.; Beausoleil, R. G.; Munro, W. J.
2007-03-15
Random-bit generators (RBGs) are key components of a variety of information processing applications ranging from simulations to cryptography. In particular, cryptographic systems require 'strong' RBGs that produce high-entropy bit sequences, but traditional software pseudo-RBGs have very low entropy content and therefore are relatively weak for cryptography. Hardware RBGs yield entropy from chaotic or quantum physical systems and therefore are expected to exhibit high entropy, but in current implementations their exact entropy content is unknown. Here we report a quantum random-bit generator (QRBG) that harvests entropy by measuring single-photon and entangled two-photon polarization states. We introduce and implement a quantum tomographic method to measure a lower bound on the 'min-entropy' of the system, and we employ this value to distill a truly random-bit sequence. This approach is secure: even if an attacker takes control of the source of optical states, a secure random sequence can be distilled.
Observable measure of quantum coherence in finite dimensional systems.
Girolami, Davide
2014-10-24
Quantum coherence is the key resource for quantum technology, with applications in quantum optics, information processing, metrology, and cryptography. Yet, there is no universally efficient method for quantifying coherence either in theoretical or in experimental practice. I introduce a framework for measuring quantum coherence in finite dimensional systems. I define a theoretical measure which satisfies the reliability criteria established in the context of quantum resource theories. Then, I present an experimental scheme implementable with current technology which evaluates the quantum coherence of an unknown state of a d-dimensional system by performing two programmable measurements on an ancillary qubit, in place of the O(d2) direct measurements required by full state reconstruction. The result yields a benchmark for monitoring quantum effects in complex systems, e.g., certifying nonclassicality in quantum protocols and probing the quantum behavior of biological complexes. PMID:25379903
Approach to design neural cryptography: A generalized architecture and a heuristic rule
NASA Astrophysics Data System (ADS)
Mu, Nankun; Liao, Xiaofeng; Huang, Tingwen
2013-06-01
Neural cryptography, a type of public key exchange protocol, is widely considered as an effective method for sharing a common secret key between two neural networks on public channels. How to design neural cryptography remains a great challenge. In this paper, in order to provide an approach to solve this challenge, a generalized network architecture and a significant heuristic rule are designed. The proposed generic framework is named as tree state classification machine (TSCM), which extends and unifies the existing structures, i.e., tree parity machine (TPM) and tree committee machine (TCM). Furthermore, we carefully study and find that the heuristic rule can improve the security of TSCM-based neural cryptography. Therefore, TSCM and the heuristic rule can guide us to designing a great deal of effective neural cryptography candidates, in which it is possible to achieve the more secure instances. Significantly, in the light of TSCM and the heuristic rule, we further expound that our designed neural cryptography outperforms TPM (the most secure model at present) on security. Finally, a series of numerical simulation experiments are provided to verify validity and applicability of our results.
Adaptive and distributed cryptography for signature biometrics protection
NASA Astrophysics Data System (ADS)
Campisi, Patrizio; Maiorana, Emanuele; Gonzalez Prats, Miguel; Neri, Alessandro
2007-02-01
The most emerging technology for people identification and authentication is biometrics. In contrast with traditional recognition approaches, biometric authentication relies on who a person is or what a person does, being based on strictly personal traits, much more difficult to be forgotten, lost, stolen, copied or forged than traditional data. In this paper, we focus on two vulnerable points of biometric systems: the database where the templates are stored and the communication channel between the stored templates and the matcher. Specifically, we propose a method, based on user adaptive error correction codes, to achieve securitization and cancelability of the stored templates applied to dynamic signature features. More in detail, the employed error correction code is tailored to the intra-class variability of each user's signature features. This leads to an enhancement of the system performance expressed in terms of false acceptance rate. Moreover, in order to avoid corruption or interception of the stored templates in the transmission channels, we propose a scheme based on threshold cryptography: the distribution of the certificate authority functionality among a number of nodes provides distributed, fault-tolerant, and hierarchical key management services. Experimental results show the effectiveness of our approach, when compared to traditional non-secure correlation-based classifiers.
Signed Decomposition Method for Scalar Multiplication in Elliptic Curve Cryptography
NASA Astrophysics Data System (ADS)
Said, M. R. M.; Mohamed, M. A.; Atan, K. A. Mohd; Zulkarnain, Z. Ahmad
2010-11-01
Addition chain is the solution to computability constraint of the problematic large number arithmetic. In elliptic curve cryptography, a point arithmetic on elliptic curve can be reduced to repetitive addition and doubling operations. Based on this idea, various methods were proposed, lately a decomposition method based on prime decomposition was put forward. This method uses a pre-generated set of rules to calculate an addition chain for n. Though the method shows it own advantage over others in some cases, but some improvements is still avail. We develop an enhancement version called signed decomposition method which takes rule from decomposition method as an input. We also generalize the idea of a prime rule to an integer rule. An improvement is done to the original add rule in decomposition method by allowing subtraction operation to terms. In so doing, we optimize the original form of add rule. The result shows not only an improvement over decomposition method but also become an all time superior compare to preceeding methods. Furthermore, having secret key in a form of rule will put up extra security to the message under communication.
Virtual microscopy and public-key cryptography for Internet telepathology.
Strauss, J S; Felten, C L; Okada, D H; Marchevsky, A M
1999-01-01
The Internet is a potentially inexpensive, widely available medium for telepathology, but there are concerns about its reliability and security. Using a digital camera, 41 photomicrographs of transbronchial biopsies, at x 100 optical magnification, were captured and digitized at 2700 x 3400 pixel, 24 bit/pixel resolution. The image files were saved in JPEG format at medium compression, attached to text files with patient information, encrypted for security in the S/MIME format using a digital signature and digital envelope, and transmitted by email. Received email files were decrypted automatically and the images viewed with standard software. Telepathology diagnoses were compared with original interpretations. The images averaged 810 kByte in size. The encryption and decryption did not cause significant delays in overall transmission time and, together with transmission, did not produce noticeable image degradation. The received image files could be viewed in a manner that simulated light microscopy. There was agreement between telepathology and original diagnoses in 92% of the cases. All the discrepancies were due to inadequate area selection because the pathological features of interest were present in histological levels other than those photographed. The use of high-resolution digital photomicrography, the Internet and public-key cryptography offers an effective and relatively inexpensive method of telepathology consultation. The method is best suited for the diagnosis of small biopsy specimens that require the transmission of only a few digital images that represent the majority of the biopsy materials. PMID:10628020
Quantum technology and cryptology for information security
NASA Astrophysics Data System (ADS)
Naqvi, Syed; Riguidel, Michel
2007-04-01
Cryptology and information security are set to play a more prominent role in the near future. In this regard, quantum communication and cryptography offer new opportunities to tackle ICT security. Quantum Information Processing and Communication (QIPC) is a scientific field where new conceptual foundations and techniques are being developed. They promise to play an important role in the future of information Security. It is therefore essential to have a cross-fertilizing development between quantum technology and cryptology in order to address the security challenges of the emerging quantum era. In this article, we discuss the impact of quantum technology on the current as well as future crypto-techniques. We then analyse the assumptions on which quantum computers may operate. Then we present our vision for the distribution of security attributes using a novel form of trust based on Heisenberg's uncertainty; and, building highly secure quantum networks based on the clear transmission of single photons and/or bundles of photons able to withstand unauthorized reading as a result of secure protocols based on the observations of quantum mechanics. We argue how quantum cryptographic systems need to be developed that can take advantage of the laws of physics to provide long-term security based on solid assumptions. This requires a structured integration effort to deploy quantum technologies within the existing security infrastructure. Finally, we conclude that classical cryptographic techniques need to be redesigned and upgraded in view of the growing threat of cryptanalytic attacks posed by quantum information processing devices leading to the development of post-quantum cryptography.
Information security: from classical to quantum
NASA Astrophysics Data System (ADS)
Barnett, Stephen M.; Brougham, Thomas
2012-09-01
Quantum cryptography was designed to provide a new approach to the problem of distributing keys for private-key cryptography. The principal idea is that security can be ensured by exploiting the laws of quantum physics and, in particular, by the fact that any attempt to measure a quantum state will change it uncontrollably. This change can be detected by the legitimate users of the communication channel and so reveal to them the presence of an eavesdropper. In this paper I explain (briefly) how quantum key distribution works and some of the progress that has been made towards making this a viable technology. With the principles of quantum communication and quantum key distribution firmly established, it is perhaps time to consider how efficient it can be made. It is interesting to ask, in particular, how many bits of information might reasonably be encoded securely on each photon. The use of photons entangled in their time of arrival might make it possible to achieve data rates in excess of 10 bits per photon.
Entangled states in quantum mechanics
NASA Astrophysics Data System (ADS)
Ruža, Jānis
2010-01-01
In some circles of quantum physicists, a view is maintained that the nonseparability of quantum systems-i.e., the entanglement-is a characteristic feature of quantum mechanics. According to this view, the entanglement plays a crucial role in the solution of quantum measurement problem, the origin of the “classicality” from the quantum physics, the explanation of the EPR paradox by a nonlocal character of the quantum world. Besides, the entanglement is regarded as a cornerstone of such modern disciplines as quantum computation, quantum cryptography, quantum information, etc. At the same time, entangled states are well known and widely used in various physics areas. In particular, this notion is widely used in nuclear, atomic, molecular, solid state physics, in scattering and decay theories as well as in other disciplines, where one has to deal with many-body quantum systems. One of the methods, how to construct the basis states of a composite many-body quantum system, is the so-called genealogical decomposition method. Genealogical decomposition allows one to construct recurrently by particle number the basis states of a composite quantum system from the basis states of its forming subsystems. These coupled states have a structure typical for entangled states. If a composite system is stable, the internal structure of its forming basis states does not manifest itself in measurements. However, if a composite system is unstable and decays onto its forming subsystems, then the measurables are the quantum numbers, associated with these subsystems. In such a case, the entangled state has a dynamical origin, determined by the Hamiltonian of the corresponding decay process. Possible correlations between the quantum numbers of resulting subsystems are determined by the symmetries-conservation laws of corresponding dynamical variables, and not by the quantum entanglement feature.
Network-Centric Quantum Communications
NASA Astrophysics Data System (ADS)
Hughes, Richard
2014-03-01
Single-photon quantum communications (QC) offers ``future-proof'' cryptographic security rooted in the laws of physics. Today's quantum-secured communications cannot be compromised by unanticipated future technological advances. But to date, QC has only existed in point-to-point instantiations that have limited ability to address the cyber security challenges of our increasingly networked world. In my talk I will describe a fundamentally new paradigm of network-centric quantum communications (NQC) that leverages the network to bring scalable, QC-based security to user groups that may have no direct user-to-user QC connectivity. With QC links only between each of N users and a trusted network node, NQC brings quantum security to N2 user pairs, and to multi-user groups. I will describe a novel integrated photonics quantum smartcard (``QKarD'') and its operation in a multi-node NQC test bed. The QKarDs are used to implement the quantum cryptographic protocols of quantum identification, quantum key distribution and quantum secret splitting. I will explain how these cryptographic primitives are used to provide key management for encryption, authentication, and non-repudiation for user-to-user communications. My talk will conclude with a description of a recent demonstration that QC can meet both the security and quality-of-service (latency) requirements for electric grid control commands and data. These requirements cannot be met simultaneously with present-day cryptography.
Quantum cloning disturbed by thermal Davies environment
NASA Astrophysics Data System (ADS)
Dajka, Jerzy; Łuczka, Jerzy
2016-03-01
A network of quantum gates designed to implement universal quantum cloning machine is studied. We analyze how thermal environment coupled to auxiliary qubits, `blank paper' and `toner' required at the preparation stage of copying, modifies an output fidelity of the cloner. Thermal environment is described in terms of the Markovian Davies theory. We show that such a cloning machine is not universal any more but its output is independent of at least a part of parameters of the environment. As a case study, we consider cloning of states in a six-state cryptography's protocol. We also briefly discuss cloning of arbitrary input states.
Secret sharing based on quantum Fourier transform
NASA Astrophysics Data System (ADS)
Yang, Wei; Huang, Liusheng; Shi, Runhua; He, Libao
2013-07-01
Secret sharing plays a fundamental role in both secure multi-party computation and modern cryptography. We present a new quantum secret sharing scheme based on quantum Fourier transform. This scheme enjoys the property that each share of a secret is disguised with true randomness, rather than classical pseudorandomness. Moreover, under the only assumption that a top priority for all participants (secret sharers and recovers) is to obtain the right result, our scheme is able to achieve provable security against a computationally unbounded attacker.
Quantum cloning disturbed by thermal Davies environment
NASA Astrophysics Data System (ADS)
Dajka, Jerzy; Łuczka, Jerzy
2016-06-01
A network of quantum gates designed to implement universal quantum cloning machine is studied. We analyze how thermal environment coupled to auxiliary qubits, `blank paper' and `toner' required at the preparation stage of copying, modifies an output fidelity of the cloner. Thermal environment is described in terms of the Markovian Davies theory. We show that such a cloning machine is not universal any more but its output is independent of at least a part of parameters of the environment. As a case study, we consider cloning of states in a six-state cryptography's protocol. We also briefly discuss cloning of arbitrary input states.
NASA Astrophysics Data System (ADS)
Zhang, KeJia; Zhang, Long; Song, TingTing; Yang, YingHui
2016-06-01
In this paper, we propose certain different design ideas on a novel topic in quantum cryptography — quantum operation sharing (QOS). Following these unique ideas, three QOS schemes, the "HIEC" (The scheme whose messages are hidden in the entanglement correlation), "HIAO" (The scheme whose messages are hidden with the assistant operations) and "HIMB" (The scheme whose messages are hidden in the selected measurement basis), have been presented to share the single-qubit operations determinately on target states in a remote node. These schemes only require Bell states as quantum resources. Therefore, they can be directly applied in quantum networks, since Bell states are considered the basic quantum channels in quantum networks. Furthermore, after analyse on the security and resource consumptions, the task of QOS can be achieved securely and effectively in these schemes.
Uncertainty characteristics of generalized quantum measurements
NASA Astrophysics Data System (ADS)
Hofmann, Holger F.
2003-02-01
The effects of any quantum measurement can be described by a collection of measurement operators {Mm} acting on the quantum state of the measured system. However, the Hilbert space formalism tends to obscure the relationship between the measurement results and the physical properties of the measured system. In this paper, a characterization of measurement operators in terms of measurement resolution and disturbance is developed. It is then possible to formulate uncertainty relations for the measurement process that are valid for arbitrary input states. The motivation of these concepts is explained from a quantum communication viewpoint. It is shown that the intuitive interpretation of uncertainty as a relation between measurement resolution and disturbance provides a valid description of measurement back action. Possible applications to quantum cryptography, quantum cloning, and teleportation are discussed.
Teleporting photonic qudits using multimode quantum scissors
NASA Astrophysics Data System (ADS)
Goyal, Sandeep K.; Konrad, Thomas
2013-12-01
Teleportation plays an important role in the communication of quantum information between the nodes of a quantum network and is viewed as an essential ingredient for long-distance Quantum Cryptography. We describe a method to teleport the quantum information carried by a photon in a superposition of a number d of light modes (a ``qudit'') by the help of d additional photons based on transcription. A qudit encoded into a single excitation of d light modes (in our case Laguerre-Gauss modes which carry orbital angular momentum) is transcribed to d single-rail photonic qubits, which are spatially separated. Each single-rail qubit consists of a superposition of vacuum and a single photon in each one of the modes. After successful teleportation of each of the d single-rail qubits by means of ``quantum scissors'' they are converted back into a qudit carried by a single photon which completes the teleportation scheme.
Teleporting photonic qudits using multimode quantum scissors.
Goyal, Sandeep K; Konrad, Thomas
2013-01-01
Teleportation plays an important role in the communication of quantum information between the nodes of a quantum network and is viewed as an essential ingredient for long-distance Quantum Cryptography. We describe a method to teleport the quantum information carried by a photon in a superposition of a number d of light modes (a "qudit") by the help of d additional photons based on transcription. A qudit encoded into a single excitation of d light modes (in our case Laguerre-Gauss modes which carry orbital angular momentum) is transcribed to d single-rail photonic qubits, which are spatially separated. Each single-rail qubit consists of a superposition of vacuum and a single photon in each one of the modes. After successful teleportation of each of the d single-rail qubits by means of "quantum scissors" they are converted back into a qudit carried by a single photon which completes the teleportation scheme. PMID:24352610
Quantum rewinding via phase estimation
NASA Astrophysics Data System (ADS)
Tabia, Gelo Noel
2015-03-01
In cryptography, the notion of a zero-knowledge proof was introduced by Goldwasser, Micali, and Rackoff. An interactive proof system is said to be zero-knowledge if any verifier interacting with an honest prover learns nothing beyond the validity of the statement being proven. With recent advances in quantum information technologies, it has become interesting to ask if classical zero-knowledge proof systems remain secure against adversaries with quantum computers. The standard approach to show the zero-knowledge property involves constructing a simulator for a malicious verifier that can be rewinded to a previous step when the simulation fails. In the quantum setting, the simulator can be described by a quantum circuit that takes an arbitrary quantum state as auxiliary input but rewinding becomes a nontrivial issue. Watrous proposed a quantum rewinding technique in the case where the simulation's success probability is independent of the auxiliary input. Here I present a more general quantum rewinding scheme that employs the quantum phase estimation algorithm. This work was funded by institutional research grant IUT2-1 from the Estonian Research Council and by the European Union through the European Regional Development Fund.
Entanglement purification for quantum communication
NASA Astrophysics Data System (ADS)
Pan, Jian-Wei; Simon, Christoph; Brukner, Časlav; Zeilinger, Anton
2001-04-01
The distribution of entangled states between distant locations will be essential for the future large-scale realization of quantum communication schemes such as quantum cryptography and quantum teleportation. Because of unavoidable noise in the quantum communication channel, the entanglement between two particles is more and more degraded the further they propagate. Entanglement purification is thus essential to distil highly entangled states from less entangled ones. Existing general purification protocols are based on the quantum controlled-NOT (CNOT) or similar quantum logic operations, which are very difficult to implement experimentally. Present realizations of CNOT gates are much too imperfect to be useful for long-distance quantum communication. Here we present a scheme for the entanglement purification of general mixed entangled states, which achieves 50 per cent of the success probability of schemes based on the CNOT operation, but requires only simple linear optical elements. Because the perfection of such elements is very high, the local operations necessary for purification can be performed with the required precision. Our procedure is within the reach of current technology, and should significantly simplify the implementation of long-distance quantum communication.