Tesis sobre el tema "Quantum cryptographic protocols"
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Ghorai, Shouvik. "Continuous-variable quantum cryptographic protocols". Electronic Thesis or Diss., Sorbonne université, 2021. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2021SORUS007.pdf.
Texto completoThis thesis is concerned with the study and analysis of two quantum cryptographic protocols: quantum key distribution (QKD) and unforgeable quantum money in the continuous-variable (CV) framework. The main advantage of CV protocols is that their implementation only requires standard telecom components. QKD allows two distant parties, Alice and Bob, to establish a secure key, even in the presence of an eavesdropper, Eve. The remarkable property of QKD is that its security can be established in the information-theoretic setting, without appealing to any computational assumptions. Proving the security of CV-QKD protocols is challenging since the protocols are described in an infinite-dimensional Fock space. One of the open questions in CV-QKD was establishing security for two-way QKD protocols against general attacks. We exploit the invariance of Unitary group U(n) of the protocol to establish composable security against general attacks. We answer another pressing question in the field of CV-QKD with a discrete modulation by establishing the asymptotic security of such protocols against collective attacks. We provide a general technique to derive a lower bound on the secret key rate by formulating the problem as a semidefinite program. Quantum money exploits the no-cloning property of quantum mechanics to generate unforgeable tokens, banknotes, and credit cards. We propose a CV private-key quantum money scheme with classical verification. The motivation behind this protocol is to facilitate the process of practical implementation. Previous classical verification money schemes use single-photon detectors for verification, while our protocols use coherent detection
Lamoureux, Louis-Philippe. "Theoretical and experimental aspects of quantum cryptographic protocols". Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210776.
Texto completo
La présente dissertation a pour but de mettre en avance ces potentiels, tant dans le domaine théorique qu’expérimental. Plus précisément, dans un premier temps, nous étudierons des protocoles de communication quantique et démontrerons que ces protocoles offrent des avantages de sécurité qui n’ont pas d’égaux en communication classique. Dans un deuxième temps nous étudierons trois problèmes spécifiques en clonage quantique ou chaque solution
apportée pourrait, à sa façon, être exploitée dans un problème de communication quantique.
Nous débuterons par décrire de façon théorique le premier protocole de communication quantique qui a pour but la distribution d’une clé secrète entre deux parties éloignées. Ce chapitre nous permettra d’introduire plusieurs concepts et outils théoriques qui seront nécessaires dans les chapitres successifs. Le chapitre suivant servira aussi d’introduction, mais cette fois-ci penché plutôt vers le côté expériemental. Nous présenterons une élégante technique qui nous permettra d’implémenter des protocoles de communication quantique de façon simple. Nous décrirons ensuite des expériences originales de communication quantique basées sur cette technique. Plus précisément, nous introduirons le concept de filtration d’erreur et utiliserons cette technique afin d’implémenter une distribution de clé quantique bruyante qui ne pourrait pas être sécurisé sans cette technique. Nous démontrerons ensuite des expériences implémentant le tirage au sort quantique et d’identification quantique.
Dans un deuxième temps nous étudierons des problèmes de clonage quantique basé sur le formalisme introduit dans le chapitre d’introduction. Puisqu’il ne sera pas toujours possible de prouver l’optimalité de nos solutions, nous introduirons une technique numérique qui nous
permettra de mettre en valeur nos résultats.
Doctorat en sciences, Spécialisation physique
info:eu-repo/semantics/nonPublished
Mamann, Hadriel. "Cold-atomic ensemble implemented as an efficient optical quantum memory layer in a cryptographic protocol". Electronic Thesis or Diss., Sorbonne université, 2024. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2024SORUS120.pdf.
Texto completoCombining cryptographic protocols with quantum memories is an important step for quantum network development in order to establish secure communications where information can be stored and retrieved on demand. One possible use case of these networks is to perform authenticated transactions synchronized by the use of memories. However, the losses and noise added by storage devices can be exploited by dishonest agents to hide their cheating attempts. The constraints to operate in a secure regime are thus very demanding in terms of memory efficiency and fidelity. This thesis focuses on the implementation of a cold-atomic ensemble used as an EIT-based quantum memory in a cryptographic protocol. The key ingredients to optimize the storage-and-retrieval efficiency and the method employed to mitigate the decoherence sources are detailed. This work reports the first demonstration of the unforgeable quantum money including an intermediate quantum memory layer, taking advantage of our highly-efficient and low-noise storage platform. The next step would be to spatially multiplex the atomic cloud in order to store the whole sequence of random qubits at once. In this scenario, the multimode capacity of our memory has been numerically simulated using two different spatial multiplexing techniques
Chailloux, André. "Quantum coin flipping and bit commitment : optimal bounds, pratical constructions and computational security". Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112121/document.
Texto completoQuantum computing allows us to revisit the study of quantum cryptographic primitives with information theoretic security. In 1984, Bennett and Brassard presented a protocol of quantum key distribution. In this protocol, Alice and Bob cooperate in order to share a common secret key k, which has to be unknown for a third party that has access to the communication channel. They showed how to perform this task quantumly with an information theoretic security; which is impossible classically.In my thesis, I study cryptographic primitives with two players that do not trust each other. I study mainly coin flipping and bit commitment. Classically, both these primitives are impossible classically with information theoretic security. Quantum protocols for these primitives where constructed where cheating players could cheat with probability stricly smaller than 1. However, Lo, Chau and Mayers showed that these primitives are impossible to achieve perfectly even quantumly if one requires information theoretic security. I study to what extent imperfect protocols can be done in this setting.In the first part, I construct a quantum coin flipping protocol with cheating probabitlity of 1/root(2) + eps for any eps > 0. This completes a result by Kitaev who showed that in any quantum coin flipping protocol, one of the players can cheat with probability at least 1/root(2). I also constructed a quantum bit commitment protocol with cheating probability 0.739 + eps for any eps > 0 and showed that this protocol is essentially optimal. I also derived some upper and lower bounds for quantum oblivious transfer, which is a universal cryptographic primitive.In the second part, I study some practical aspects related to these primitives. I take into account losses than can occur when measuring a quantum state. I construct a Quantum Coin Flipping and Quantum Bit Commitment protocols which are loss-tolerant and have cheating probabilities of 0.859. I also construct these primitives in the device independent model, where the players do not trust their quantum device. Finally, in the third part, I study these cryptographic primitives with information theoretic security. More precisely, I study the relationship between computational quantum bit commitment and quantum zero-knowledge protocols
BIN, ALI NORSHAMSURI. "Implementation of Quantum Cryptography Protocol". Doctoral thesis, Università degli Studi di Camerino, 2014. http://hdl.handle.net/11581/401770.
Texto completoColisson, Léo. "Study of Protocols Between Classical Clients and a Quantum Server". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS105.
Texto completoQuantum computers promise surprising powers of computation by exploiting the stunning physical properties of infinitesimally small particles. I focused on designing and proving the security of protocols that allow a purely classical client to use the computational resources of a quantum server, so that the performed computation is never revealed to the server. To this end, I develop a modular tool to generate on a remote server a quantum state that only the client is able to describe, and I show how multi-qubits quantum states can be generated more efficiently. I also prove that there is no such protocol that is secure in a generally composable model of security, including when our module is used in the UBQC protocol. In addition to delegated computation, this tool also proves to be useful for performing a task that might seem impossible to achieve at first sight: proving advanced properties on a quantum state in a non-interactive and non-destructive way, including when this state is generated collaboratively by several participants. This can be seen as a quantum analogue of the classical Non-Interactive Zero-Knowledge proofs. This property is particularly useful to filter the participants of a protocol without revealing their identity, and may have applications in other domains, for example to transmit a quantum state over a network while hiding the source and destination of the message. Finally, I discuss my ongoing independent work on One-Time Programs, mixing quantum cryptography, error correcting codes and information theory
Neves, Simon. "Photonic Resources for the Implementation of Quantum Network Protocols". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS364.
Texto completoThe security of modern communication networks can be enhanced thanks to the laws of quantum mechanics. In this thesis, we develop a source of photon-pairs, emitted via spontaneous parametric down-conversion, which we use to demonstrate new quantum-cryptographic primitives. Pairs are used as heralded single-photons or as close-to-maximally entangled pairs. We also provide a novel design in order to adapt this source to multipartite entanglement generation. We provide the first experimental implementation of quantum weak coin flipping protocol. It allows two distant players to decide of a random winner. We demonstrate a refined and loss-tolerent version of a recently proposed theoretical protocol, using heralded single-photons mixed with vacuum to produce entanglement. It displays cheat-sensitivity, allowed by quantum interference and a fast optical switch. We also provide a new protocol for certifying the transmission of an unmeasured qubit through a lossy and untrusted channel. The security is based on new fundamental results of lossy quantum channels. We device-independently test the channel’s quality, using self-testing of Bell or steering inequalities thanks to photon-pairs entangled in polarization to probe the channel. We show it allows the certification of quantum communication for a large amount of losses induced by the channel
Music, Luka. "Multi-Party Quantum Cryptography : from Folklore to Real-World". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS412.
Texto completoQuantum cryptography builds upon decades of advances both in classical cryptography and networks. However, contrary to its classical counterparts, it is still in its infancy applicability-wise, even in the scenario where powerful quantum computers are readily available, and more theoretical work is required before it can provide concrete benefits. The first goal is to formalise in rigorous quantum security frameworks the properties of various techniques that have been transposed, often without proper justification, from the classical world.Then, the recent developments in quantum technologies suggest a mostly cloud-based future availability of quantum devices. Therefore, quantum computation and communication cost of protocol participants must be lowered before being useful.Finally, in most situations, additional steps need to be taken to tailor protocols to the specifications of devices. This allows for optimisations both in terms of quantum memory and operation requirements.This thesis contributes to these three aspects by: (i) giving the first general security definition of the Quantum Cut-and-Choose, a technique for proving the correctness of a quantum message; (ii) presenting a more realistic framework of security against superposition attacks, where classical protocols run on inherently quantum devices; (iii) constructing an efficient delegated multi-party quantum computation protocol, allowing clients to delegate securely to a quantum server a private computation; (iv) building a method for verifying the honesty of a quantum server performing computations on behalf of a client with no operation or memory overhead compared to the unprotected computation
Javelle, Jérôme. "Cryptographie Quantique : Protocoles et Graphes". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENM093/document.
Texto completoI want to realize an optimal theoretical model for quantum secret sharing protocols based on graph states. The main parameter of a threshold quantum secret sharing scheme is the size of the largest set of players that can not access the secret. Thus, my goal is to find a collection of protocols for which the value of this parameter is the smallest possible. I also study the links between quantum secret sharing protocols and families of curves in algebraic geometry
Zhang, Zheshen. "Quantum key distribution protocols with high rates and low costs". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28240.
Texto completoCalisti, Davide. "Performance Analysis and Multi-hop Protocols for Quantum Cryptography based on BB84". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Buscar texto completoAlvila, Markus. "A Performance Evaluation of Post-Quantum Cryptography in the Signal Protocol". Thesis, Linköpings universitet, Informationskodning, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158244.
Texto completoTale, kalachi Herve. "Sécurité des protocoles cryptographiques fondés sur la théorie des codes correcteurs d'erreurs". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR045/document.
Texto completoContrary to the cryptosystems based on number theory, the security of cryptosystems based on error correcting codes appears to be resistant to the emergence of quantum computers. Another advantage of these systems is that the encryption and decryption are very fast, about five times faster for encryption, and 10 to 100 times faster for decryption compared to RSA cryptosystem. Nowadays, the interest of scientific community in code-based cryptography is highly motivated by the latest announcement of the National Institute of Standards and Technology (NIST). They initiated the Post-Quantum cryptography Project which aims to define new standards for quantum resistant cryptography and fixed the deadline for public key cryptographic algorithm submissions for November 2017. This announcement motivates to study the security of existing schemes in order to find out whether they are secure. This thesis thus presents several attacks which dismantle several code-based encryption schemes. We started by a cryptanalysis of a modified version of the Sidelnikov cryptosystem proposed by Gueye and Mboup [GM13] which is based on Reed-Muller codes. This modified scheme consists in inserting random columns in the secret generating matrix or parity check matrix. The cryptanalysis relies on the computation of the square of the public code. The particular nature of Reed-Muller which are defined by means of multivariate binary polynomials, permits to predict the values of the dimensions of the square codes and then to fully recover in polynomial time the secret positions of the random columns. Our work shows that the insertion of random columns in the Sidelnikov scheme does not bring any security improvement. The second result is an improved cryptanalysis of several variants of the GPT cryptosystem which is a rank-metric scheme based on Gabidulin codes. We prove that any variant of the GPT cryptosystem which uses a right column scrambler over the extension field as advocated by the works of Gabidulin et al. [Gab08, GRH09, RGH11] with the goal to resist Overbeck’s structural attack [Ove08], are actually still vulnerable to that attack. We show that by applying the Frobeniusoperator appropriately on the public key, it is possible to build a Gabidulin code having the same dimension as the original secret Gabidulin code, but with a lower length. In particular, the code obtained by this way corrects less errors than thesecret one but its error correction capabilities are beyond the number of errors added by a sender, and consequently an attacker is able to decrypt any ciphertext with this degraded Gabidulin code. We also considered the case where an isometrictransformation is applied in conjunction with a right column scrambler which has its entries in the extension field. We proved that this protection is useless both in terms of performance and security. Consequently, our results show that all the existingtechniques aiming to hide the inherent algebraic structure of Gabidulin codes have failed. To finish, we studied the security of the Faure-Loidreau encryption scheme [FL05] which is also a rank-metric scheme based on Gabidulin codes. Inspired by our precedent work and, although the structure of the scheme differs considerably from the classical setting of the GPT cryptosystem, we show that for a range of parameters, this scheme is also vulnerable to a polynomial-time attack that recovers the private key by applying Overbeck’s attack on an appropriate public code. As an example we break in a few seconds parameters with 80-bit security claim
Oniki, Chiquito Izumi 1985. "Protocolos criptográficos de identificação baseados em reticulados". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/275648.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação
Made available in DSpace on 2018-08-22T11:38:01Z (GMT). No. of bitstreams: 1 OnikiChiquito_Izumi_M.pdf: 3419663 bytes, checksum: 5f621e251ebc62429a85ff141091f7f5 (MD5) Previous issue date: 2012
Resumo: Na área de Segurança da Informação, controle de acesso diz respeito á habilidade de permitir ou negar a utilização de determinados recursos, sejam eles informações, dispositivos, serviços etc., por parte de um indivíduo. Protocolos de identificação correspondem a algoritmos criptográficos que permitem verificar, com certo grau de confiança, se a alegação de um indivíduo a respeito de sua identidade é verdadeira. Dessa forma, pode-se prover acesso controlado e conceder privilégios de utilização de recursos somente a entidades ou indivíduos cuja identidade tenha sido comprovada. Algoritmos baseados em reticulados, de uma forma geral, têm despertado particular interesse em aplicações criptográficas, devido à sua provável resistência a ataques empregando computadores quânticos, ao contrário dos criptossistemas baseados em problemas da Teoria dos Números. Por esse motivo, nos _últimos anos, tem-se buscado desenvolver protocolos de identificação cuja segurança esteja relacionada a problemas envolvendo reticulados. Neste trabalho, foram abordadas as principais propostas recentes de protocolos de identificação baseados em reticulados. Além da apresentação dos algoritmos, é feita uma análise comparativa entre protocolos selecionados, incorporando dados experimentais de execução. A etapa de implementação aqui apresentada tem também como finalidade suprir a ausência de resultados experimentais para essa categoria de protocolos, no sentido de iniciar um processo de validação para uso dos algoritmos em aplicações práticas. Questões como possibilidades de otimização e expectativas para o futuro da área também são discutidas
Abstract: One of the main concerns of the field of Information Security is access control, which refers to the restriction of access to several kinds of resources, such as data, places, devices, services and others. Identification schemes are cryptographic algorithms that allow verifying with some level of certainty if an identity claim is legitimate. Therefore, such schemes make possible to provide access control and grant privileges only to authorized individuals whose identities have been previously verified. Lattice-based algorithms are particularly interesting as the cryptography community believes them to remain secure even to quantum computers attacks, as opposite to some cryptosystems used today based on Number Theory problems. For this reason, identification schemes based on lattices have received growing attention lately. In this work, we address the main recent developments of lattice-based identification schemes. After introducing the algorithms, we make a comparative analysis of the selected schemes, using experimental data collected from our own implementation of the algorithms. The implementation phase also aims to help validating these schemes for practical use, since to this date there were practically no experimental results available. Other issues, like optimization possibilities and the future of the area, are also addressed in this work
Mestrado
Ciência da Computação
Mestra em Ciência da Computação
Richmond, Tania. "Implantation sécurisée de protocoles cryptographiques basés sur les codes correcteurs d'erreurs". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES048/document.
Texto completoThe first cryptographic protocol based on error-correcting codes was proposed in 1978 by Robert McEliece. Cryptography based on codes is called post-quantum because until now, no algorithm able to attack this kind of protocols in polynomial time, even using a quantum computer, has been proposed. This is in contrast with protocols based on number theory problems like factorization of large numbers, for which efficient Shor's algorithm can be used on quantum computers. Nevertheless, the McEliece cryptosystem security is based not only on mathematical problems. Implementation (in software or hardware) is also very important for its security. Study of side-channel attacks against the McEliece cryptosystem have begun in 2008. Improvements can still be done. In this thesis, we propose new attacks against decryption in the McEliece cryptosystem, used with classical Goppa codes, including corresponding countermeasures. Proposed attacks are based on evaluation of execution time of the algorithm or its power consumption analysis. Associate countermeasures are based on mathematical and algorithmic properties of the underlying algorithm. We show that it is necessary to secure the decryption algorithm by considering it as a whole and not only step by step
Leifgen, Matthias. "Protocols and components for quantum key distribution". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17473.
Texto completoIn this thesis, photonic quantum states are used for experimental realisations of two different concepts of quantum information processing. Quantum key distribution (QKD) is revolutionary because it is the only cryptographic scheme offering unconditional security. Two major problems prevail: Firstly, matching the conditions for unconditional security is challenging, secondly, long distance communication beyond 200 km is very demanding because an increasingly attenuated quantum state starts to fail the competition with constant noise. One experiment accomplished in this thesis is concerned with the first problem. The realisation of the actual quantum state is critical. Single photon states from nitrogen and for the first time also silicon vacancy defect centres are used for a QKD transmission under the BB84 (Bennett and Brassard 1984). The deviation of the used single photon states from the ideal state is thoroughly investigated and the information an eavesdropper obtains due to this deviation is analysed. Transmitting quantum states via satellites is a potential solution to the limited achievable distances in QKD. A novel protocol particularly suited for this is implemented for the first time in this thesis, the frequency-time (FT) protocol. The protocol is thoroughly investigated by varying the experimental parameters over a wide range and by evaluating the impact on the performance and the security. Finally, big steps towards a fully automated fibre-based BB84 QKD experiment in the time-bin implementation with autonomous sender and receiver units are accomplished. Another important concept using quantum mechanical properties as a resource is a quantum random number generator (QRNG). Random numbers are used for various applications in computing and cryptography. A QRNG supplying bits with high and quantifiable randomness at a record-breaking rate is reported and the statistical properties of the random output is thoroughly tested.
Frixons, Paul. "Cryptographie à clé secrète et attaquant quantique dans le monde des télécommunications". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS339.
Texto completoFor modern cryptography, the security of a system is defined as the sum of the resources required to break it. With the advent of efficient quantum computers and the new algorithmic possibilities that this opens, this amount of resource is destined to change.In this thesis, we take a step towards a better understanding of this quantum threat. After an introduction to quantum computation and cryptography, we show quantum attacks against the Legendre PRF in the setting without superposition queries and reduced quantum memory. Afterwards, we present a general way to transpose boomerang attacks into quantum attacks as well as some applications. We continue on a doubling method for block ciphers inspired by the Encrypt-Mix-Encrypt scheme and prove its security. We end by building a quantum version of the 3G/4G/5G UMTS-AKA authentication protocol before showing the security as well as the underlying primitives Milenage and TUAK
Toulemonde, Ambre. "Study of consensus protocols for blockchain technologies and quantum cryptanalysis of Misty schemes". Electronic Thesis or Diss., université Paris-Saclay, 2022. http://www.theses.fr/2022UPASG041.
Texto completoIn recent years, two research domains in cryptography have received considerable attention: consensus protocols for blockchain technologies due to the emergence of cryptocurrencies, and quantum cryptanalysis due to the threat of quantum computers. Naturally, our research topics are geared towards these two research domains that are studied separately in this thesis.In the first part, we analyze the security of consensus protocols which are one of main challenges in these technologies. We focus more specifically on the leader election of consensus protocols. After a study of the state of the art on consensus protocols before and after the emergence of blockchain technologies, we study the security of two promising approaches to construct these protocols, called Algorand and Single Secret Leader Election. As a result, we define a security model of leader election with five security properties that address well-known issues and attacks against consensus protocols. Then, we provide a new leader election protocol called LEP-TSP intended to be used in private setting and prove that LEP-TSP meets the expected security properties while more than two third of participants are honest. As additional work, we provide a high level description of a new consensus protocol called Useful Work that uses the computing power to solve any real world problem.In the second part of this thesis, we review the best known cryptanalysis results on Misty schemes and we provide new quantum cryptanalysis results. First, we describe non-adaptive quantum chosen plaintext attacks (QCPA) against 4-round Misty L, 4-round Misty LKF, 3-round Misty R and 3-round Misty RKF schemes. We extend the QCPA attack against 3-round Misty RKF schemes to recover the keys of d-round Misty RKF schemes. As additional work, we show that the best known non-quantum attack against 3-round Misty R schemes is optimal
Pappa, Anna. "Protocoles de chiffrement quantiques de plusieurs parties en environnements réalistes". Electronic Thesis or Diss., Paris, ENST, 2014. http://www.theses.fr/2014ENST0045.
Texto completoThis thesis stands at the interface between quantum theory and experiments, focusing on practical protocols that can be implemented using present-day technology. Our goal is to build a general framework for the design and implementation of quantum cryptographic schemes that will improve the safety of future telecommunication networks. In addition, this thesis aims to advance research on quantum physics and computer science, by improving our understanding of entanglement. The correlations of entangled states can not be reproduced by conventional means, allowing to perform tasks (eg teleportation and superdense coding) that are otherwise impossible. It is therefore of major importance to be able to check whether a quantum state is entangled. In this thesis, we show how to efficiently check whether a physical source can create multi-party entangled states and share them with many parties, some of which are dishonest and work with the source. This protocol could prove essential for quantum computation between suspicious parties and could also facilitate the secure delegation of tasks to powerful untrusted quantum servers. Finally, we study the link between game theory and quantum non-locality, in the context of Bayesian games. We examine how the shared entanglement helps players win a game with a higher probability than the conventional resources could achieve
Pappa, Anna. "Protocoles de chiffrement quantiques de plusieurs parties en environnements réalistes". Thesis, Paris, ENST, 2014. http://www.theses.fr/2014ENST0045/document.
Texto completoThis thesis stands at the interface between quantum theory and experiments, focusing on practical protocols that can be implemented using present-day technology. Our goal is to build a general framework for the design and implementation of quantum cryptographic schemes that will improve the safety of future telecommunication networks. In addition, this thesis aims to advance research on quantum physics and computer science, by improving our understanding of entanglement. The correlations of entangled states can not be reproduced by conventional means, allowing to perform tasks (eg teleportation and superdense coding) that are otherwise impossible. It is therefore of major importance to be able to check whether a quantum state is entangled. In this thesis, we show how to efficiently check whether a physical source can create multi-party entangled states and share them with many parties, some of which are dishonest and work with the source. This protocol could prove essential for quantum computation between suspicious parties and could also facilitate the secure delegation of tasks to powerful untrusted quantum servers. Finally, we study the link between game theory and quantum non-locality, in the context of Bayesian games. We examine how the shared entanglement helps players win a game with a higher probability than the conventional resources could achieve
Andrade, Ewerton Rodrigues. "Proposta de aprimoramento para o protocolo de assinatura digital Quartz". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-23102013-163524/.
Texto completoToday, we can see that a large dependence of the systems developed under the cryptography was introduced in all of us. Especially in terms of public key cryptosystems, which are widely used on the Internet. However, public key cryptography was threatened and began to investigate new sources of problems for their systems when Shor in 1997 developed a polynomial time algorithm for factoring integers and to compute the discrete logarithm in a quantum computer. In this context, Patarin proposed Hidden Field Equations (HFE), a trapdoor based on MQ (Multivariate Quadratic) and IP (Isomorphism of Polynomials) problems. Such problems are not affected by the Shor algorithm, moreover MQ Problem was demonstrate by Patarin and Goubin as NP-complete. Despite the basic HFE has broken, it varies secure, obtained by generic modification. The Quartz -- digital signature scheme based on HFEv-, with special choice of parameters -- is a good example of this resistance to algebraic attacks aimed at the recovery of the private key, because even today remains secure. Furthermore, it also generates short signatures. However, Joux and Martinet -- based on axioms of Birthday Paradox Attack -- proved that Quartz is malleable, showing that if the adversary has a pair (message, signature) valid, he can get a second signature with 2^(50) computations and 2^(50) calls to the signing oracle, so far the current security standards that are at least 2^(112). Thus, based on Quartz, we present a new digital signature scheme, achieving the adaptive chosen message attacks that make calls to the random oracle, with a secure level estimated at 2^(112). Our cryptosystem also provides an efficiency gain in signature verification algorithm and initialization vectors that will be used for signing and verification algorithms. Further we provide an implementation of Original Quartz and Enhanced Quartz in the Java programming language.
Monteiro, Fabio de Salles. "Protocolo de Identificação baseado em Polinômios Multivariáveis Quadráticos". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-19032013-104154/.
Texto completoThe public-key cryptography widely used nowadays have their security based on the assumption of the intractability of the problems of integer factorization and discrete logarithm, both of which were proven unsafe in the advent of quantum computers. Cryptographic systems based on Multivariate Quadratic polynomials (MQ) are based on the MQ problem, which consists in solve a system of multivariate quadratic polynomials over a finite field. The MQ problem has been proven NP-complete and so far no polynomial time algorithm is known, not even quantum, which would resolve this problem, making worthwhile to be investigated and developed as a real candidate to provide post-quantum cryptography. In CRYPTO\'2011 Sakumoto, Shirai and Hiwatari introduced two new identification protocols based on multivariate quadratic polynomials, which we call MQID-3 and MQID-5, in particular, for the first time, their security is based only on the MQ problem. Using these proposals, we will present an improved version of the protocol MQID-3 that reduces communication by approximately 9%.
Chailloux, Andre. "Quantum coin flipping and bit commitment : optimal bounds, pratical constructions and computational security". Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00607890.
Texto completoAlamelou, Quentin. "Protocoles cryptographiques pour l’authentification numérique et le respect de la vie privée". Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0042/document.
Texto completoInternet constant growth has naturally led to cryptographic issues such as authentication and privacy concerns. The common usage of connected devices (smartphones, tablet, watch, …) as authentication means made us consider cryptographic keys generations and/or managements from such devices to address aforementioned needs. For such a purpose, we identified fuzzy extractors and group signature schemes. On the one hand, this thesis then presents the first reusable fuzzy extractor based on set difference metric (in the nonprogrammable random oracle). In so doing, we were able to design a key generation module performing authentication from users’ devices. On the other hand, we came up with two group signature schemes, respectively based on Hamming and rank metrics, that seriously compete with post-quantum concurrent schemes based on lattices
Sikora, Jamie. "Analyzing Quantum Cryptographic Protocols Using Optimization Techniques". Thesis, 2012. http://hdl.handle.net/10012/6760.
Texto completoWare, Christopher J. "Modeling and analysis of quantum cryptographic protocols". Thesis, 2008. http://hdl.handle.net/1828/1103.
Texto completoTong-XuanWei y 衛彤軒. "Security Analysis on Quantum Cryptographic Protocols Based on Quantum Information Theory". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/79505488113490413997.
Texto completoFishbein, Dieter. "Machine-Level Software Optimization of Cryptographic Protocols". Thesis, 2014. http://hdl.handle.net/10012/8400.
Texto completoAkshatha, Shenoy H. "Role of Nonlocality and Counterfactuality in Quantum Cryptography". Thesis, 2014. http://etd.iisc.ac.in/handle/2005/2987.
Texto completoAkshatha, Shenoy H. "Role of Nonlocality and Counterfactuality in Quantum Cryptography". Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2987.
Texto completoCosta, Luís Esquível. "Integration of post-quantum cryptography in the TLS protocol (LWE Option)". Master's thesis, 2019. http://hdl.handle.net/1822/66926.
Texto completoWith the possibility of quantum computers making an appearance, possibly capable of breaking several well established and widespread crytposystems (especially those that implement public key cryptography), necessity has arisen to create new cryptographic algorithms which remain safe even against adversaries using quantum computers. Several algorithms based on different mathematical problems have been proposed which are considered to be hard to solve with quantum computers. In recent years, a new lattice-based mathematical problem called Learning With Errors (and its variant Ring - Learning With Errors) was introduced, and several cryptosystems based on this problem were introduced, some of which are becoming practical enough to compete with traditional schemes that have been used for decades. The primary focus in this work is the implementation of two Ring - Learning With Errors based schemes (one key exchange mechanism and one digital signature scheme) on the TLS protocol via the OpenSSL library as a way of checking their overall viability in real-world scenarios, by comparing them to classical schemes implementing the same functionalities.
Com a possibilidade do surgimento dos primeiros computadores quânticos, possivelmente capazes de quebrar muitos dos cripto-sistemas bem difundidos e considerados seguros, tornou-se necessário tomar precauções com a criação de novas técnicas criptográficas que visam manter as suas propriedades de segurança mesmo contra adversários que usem computadores quânticos. Existem já muitas propostas de algoritmos baseados em problemas matemáticos distintos que são considerados difíceis de resolver recorrendo a computadores quânticos. Recentemente, foi introduzido um novo problema baseado em reticulados denominado de Learning With Errors (e a sua variante Ring - Learning With Errors), e consequentemente foram propostos vários cripto-sistemas baseados nesse problema, alguns dos quais começam já a ser utilizáveis ao ponto de poderem ser comparados com os esquemas clássicos usados há décadas. O foco principal neste trabalho é a implementação de dois esquemas baseados no problema Ring - Learning With Errors (mais precisamente, um esquema de troca de chaves e uma assinatura digital) no protocolo TLS através da sua integração no OpenSSL como forma de verificar a sua viabilidade em contextos reais, comparando-os com esquemas clássicos que implementem as mesmas funcionalidades.
Καρύδης, Θρασύβουλος. "Κβαντικά αποτυπώματα : Θεωρία και εφαρμογές στην πολυπλοκότητα και στην ασφάλεια επικοινωνίας". Thesis, 2014. http://hdl.handle.net/10889/8047.
Texto completoFingerprints provide an elegant and cost-e ective solution to the Equality Problem in communication complexity. Their quantum counterpart is one example where an exponential gap exists between classical and quantum communication cost. Moreover, recent publications have proposed e cient ways to construct and work with quantum ngerprints in practice. Apart from the savings in communication cost, quantum ngerprints have an additional, inherent feature, namely the ability to hide information, which renders them a perfect candidate for Quantum Cryptography. This thesis reviews quantum ngerprints both as a communication complexity asset as well as a crypto-primitive and investigates the use of Quantum Fingerprinting to implement experimentally feasible Quantum Money schemes. We propose a public-key Quantum Money scheme comprising Quantum Fingerprints as well as an experimental implementation of it, feasible with current technology.