Dissertations / Theses on the topic 'Symmetric ciphers'
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1
Gustafson, Helen May. "Statistical analysis of symmetric ciphers." Thesis, Queensland University of Technology, 1996.
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2
Penna, Lyta. "Implementation issues in symmetric ciphers." Thesis, Queensland University of Technology, 2002.
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3
Mirza, Fauzan ul-Haque. "Analysis of some modern symmetric ciphers." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271702.
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4
Dawson, Edward Pyle. "Design and cryptanalysis of symmetric ciphers." Thesis, Queensland University of Technology, 1991.
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5
Henricksen, Matthew. "Design, Implementation and Cryptanalysis of Modern Symmetric Ciphers." Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16055/1/Matt_Henricksen_Thesis.pdf.
Full textAbstract:
The main objective of this thesis is to examine the trade-offs between security and
efficiency within symmetric ciphers. This includes the influence that block ciphers
have on the new generation of word-based stream ciphers. By incorporating
block-cipher like components into their designs, word-based stream ciphers have
experienced hundreds-fold improvement in speed over bit-based stream ciphers,
without any observable security degradation. The thesis also emphasizes the importance of keying issues in block and stream ciphers, showing that by reusing components of the principal cipher algorithm in the keying algorithm, security
can be enhanced without loss of key-agility or expanding footprint in software memory.
Firstly, modern block ciphers from four recent cipher competitions are surveyed and categorized according to criteria that includes the high-level structure of the block cipher, the method in which non-linearity is instilled into each round, and the strength of the key schedule. In assessing the last criterion, a classification
by Carter [45] is adopted and modified to improve its consistency.
The classification is used to demonstrate that the key schedule of the Advanced Encryption Standard (AES) [62] is surprisingly flimsy for a national standard. The claim is supported with statistical evidence that shows the key schedule suffers from bit leakage and lacks sufficient diffusion. The thesis contains a replacement key schedule that reuses components from the cipher algorithm, leveraging existing analysis to improve security, and reducing the cipher's implementation footprint while maintaining key agility. The key schedule is analyzed from the perspective of an efficiency-security tradeoff, showing that the new schedule rectifies an imbalance towards e±ciency present in the original.
The thesis contains a discussion of the evolution of stream ciphers, focusing on
the migration from bit-based to word-based stream ciphers, from which follows a commensurate improvement in design flexibility and software performance. It examines the influence that block ciphers, and in particular the AES, have had upon the development of word-based stream ciphers. The thesis includes a concise literature review of recent styles of cryptanalytic attack upon stream ciphers.
Also, claims are refuted that one prominent word-based stream cipher, RC4, suffers from a bias in the first byte of each keystream.
The thesis presents a divide and conquer attack against Alpha1, an irregularly clocked bit-based stream cipher with a 128-bit state. The dominating aspect of the divide and conquer attack is a correlation attack on the longest register. The internal state of the remaining registers is determined by utilizing biases in the clocking taps and launching a guess and determine attack. The overall complexity of the attack is 261 operations with text requirements of 35,000 bits and memory requirements of 2 29.8 bits.
MUGI is a 64-bit word-based cipher with a large Non-linear Feedback Shift Register (NLFSR) and an additional non-linear state. In standard benchmarks, MUGI appears to su®er from poor key agility because it is implemented on an
architecture for which it is not designed, and because its NLFSR is too large relative to the size of its master key. An unusual feature of its key initialization algorithm is described. A variant of MUGI, entitled MUGI-M, is proposed to
enhance key agility, ostensibly without any loss of security.
The thesis presents a new word-based stream cipher called Dragon. This cipher uses a large internal NLFSR in conjunction with a non-linear filter to produce 64 bits of keystream in one round. The non-linear filter looks very
much like the round function of a typical modern block cipher. Dragon has a native word size of 32 bits, and uses very simple operations, including addition, exclusive-or and s-boxes. Together these ensure high performance on modern day processors such as the Intel Pentium family.
Finally, a set of guidelines is provided for designing and implementing symmetric ciphers on modern processors, using the Intel Pentium 4 as a case study. Particular attention is given to understanding the architecture of the processor,
including features such as its register set and size, the throughput and latencies of its instruction set, and the memory layouts and speeds. General optimization rules are given, including how to choose fast primitives for use within the cipher. The thesis describes design decisions that were made for the Dragon cipher with respect to implementation on the Intel Pentium 4.
Block Ciphers, Word-based Stream Ciphers, Cipher Design, Cipher Implementa-
tion, -
6
Henricksen, Matthew. "Design, Implementation and Cryptanalysis of Modern Symmetric Ciphers." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16055/.
Full textAbstract:
The main objective of this thesis is to examine the trade-offs between security and efficiency within symmetric ciphers. This includes the influence that block ciphers have on the new generation of word-based stream ciphers. By incorporating block-cipher like components into their designs, word-based stream ciphers have experienced hundreds-fold improvement in speed over bit-based stream ciphers, without any observable security degradation. The thesis also emphasizes the importance of keying issues in block and stream ciphers, showing that by reusing components of the principal cipher algorithm in the keying algorithm, security can be enhanced without loss of key-agility or expanding footprint in software memory. Firstly, modern block ciphers from four recent cipher competitions are surveyed and categorized according to criteria that includes the high-level structure of the block cipher, the method in which non-linearity is instilled into each round, and the strength of the key schedule. In assessing the last criterion, a classification by Carter [45] is adopted and modified to improve its consistency. The classification is used to demonstrate that the key schedule of the Advanced Encryption Standard (AES) [62] is surprisingly flimsy for a national standard. The claim is supported with statistical evidence that shows the key schedule suffers from bit leakage and lacks sufficient diffusion. The thesis contains a replacement key schedule that reuses components from the cipher algorithm, leveraging existing analysis to improve security, and reducing the cipher's implementation footprint while maintaining key agility. The key schedule is analyzed from the perspective of an efficiency-security tradeoff, showing that the new schedule rectifies an imbalance towards e±ciency present in the original. The thesis contains a discussion of the evolution of stream ciphers, focusing on the migration from bit-based to word-based stream ciphers, from which follows a commensurate improvement in design flexibility and software performance. It examines the influence that block ciphers, and in particular the AES, have had upon the development of word-based stream ciphers. The thesis includes a concise literature review of recent styles of cryptanalytic attack upon stream ciphers. Also, claims are refuted that one prominent word-based stream cipher, RC4, suffers from a bias in the first byte of each keystream. The thesis presents a divide and conquer attack against Alpha1, an irregularly clocked bit-based stream cipher with a 128-bit state. The dominating aspect of the divide and conquer attack is a correlation attack on the longest register. The internal state of the remaining registers is determined by utilizing biases in the clocking taps and launching a guess and determine attack. The overall complexity of the attack is 261 operations with text requirements of 35,000 bits and memory requirements of 2 29.8 bits. MUGI is a 64-bit word-based cipher with a large Non-linear Feedback Shift Register (NLFSR) and an additional non-linear state. In standard benchmarks, MUGI appears to su®er from poor key agility because it is implemented on an architecture for which it is not designed, and because its NLFSR is too large relative to the size of its master key. An unusual feature of its key initialization algorithm is described. A variant of MUGI, entitled MUGI-M, is proposed to enhance key agility, ostensibly without any loss of security. The thesis presents a new word-based stream cipher called Dragon. This cipher uses a large internal NLFSR in conjunction with a non-linear filter to produce 64 bits of keystream in one round. The non-linear filter looks very much like the round function of a typical modern block cipher. Dragon has a native word size of 32 bits, and uses very simple operations, including addition, exclusive-or and s-boxes. Together these ensure high performance on modern day processors such as the Intel Pentium family. Finally, a set of guidelines is provided for designing and implementing symmetric ciphers on modern processors, using the Intel Pentium 4 as a case study. Particular attention is given to understanding the architecture of the processor, including features such as its register set and size, the throughput and latencies of its instruction set, and the memory layouts and speeds. General optimization rules are given, including how to choose fast primitives for use within the cipher. The thesis describes design decisions that were made for the Dragon cipher with respect to implementation on the Intel Pentium 4. Block Ciphers, Word-based Stream Ciphers, Cipher Design, Cipher Implementa- tion, -
7
Čanda, Valér. "Scalable symmetric block ciphers based on group bases." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962789755.
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8
Saran, Nurdan A. "Time Memory Trade Off Attack On Symmetric Ciphers." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610437/index.pdf.
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Time Memory Trade O (TMTO) is a cryptanalytic method that aims to develop an attack
which has a lower memory complexity than lookup table and a lower online time complexity
than exhaustive search. TMTO methods are widely studied in the literature and used for
inverting various cryptosystems. We focus on the design and the analysis of TMTO on symmetric
ciphers in this thesis. Firstly, the summary of the random mapping statistics from the
view point of TMTO is presented. We also recalculate some expected values with a simpler
approach than the existing proofs. Then, we propose some variant constructions and
also present three new distinguishers based on random mappings. Next, we provide a detailed
analysis of the success rate of two main improvements of the attackDistinguished Point Method and Rainbow Method. Finally, we discuss the adjustment of the parameters to achieve a high success rate. To support our theoretical framework, we also present empirical results of our analysis to actual ciphers.
9
May, Lauren Jeanette. "Design, analysis and implementation of symmetric block ciphers." Thesis, Queensland University of Technology, 2002.
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10
McKague, Matthew. "Design and Analysis of RC4-like Stream Ciphers." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/1141.
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RC4 is one of the most widely used ciphers in practical software applications. In this thesis we examine security and design aspects of RC4. First we describe the functioning of RC4 and present previously published analyses. We then present a new cipher, Chameleon which uses a similar internal organization to RC4 but uses different methods. The remainder of the thesis uses ideas from both Chameleon and RC4 to develop design strategies for new ciphers. In particular, we develop a new cipher, RC4B, with the goal of greater security with an algorithm comparable in simplicity to RC4. We also present design strategies for ciphers and two new ciphers for 32-bit processors. Finally we present versions of Chameleon and RC4B that are implemented using playing-cards.
11
Z'aba, Muhammad Reza. "Analysis of linear relationships in block ciphers." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/35725/1/Muhammad_Z%27aba_Thesis.pdf.
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This thesis is devoted to the study of linear relationships in symmetric block ciphers. A block cipher is designed so that the ciphertext is produced as a nonlinear function of the plaintext and secret master key. However, linear relationships within the cipher can still exist if the texts and components of the cipher are manipulated in a number of ways, as shown in this thesis. There are four main contributions of this thesis. The first contribution is the extension of the applicability of integral attacks from word-based to bitbased block ciphers. Integral attacks exploit the linear relationship between texts at intermediate stages of encryption. This relationship can be used to recover subkey bits in a key recovery attack. In principle, integral attacks can be applied to bit-based block ciphers. However, specific tools to define the attack on these ciphers are not available. This problem is addressed in this thesis by introducing a refined set of notations to describe the attack. The bit patternbased integral attack is successfully demonstrated on reduced-round variants of the block ciphers Noekeon, Present and Serpent. The second contribution is the discovery of a very small system of equations that describe the LEX-AES stream cipher. LEX-AES is based heavily on the 128-bit-key (16-byte) Advanced Encryption Standard (AES) block cipher. In one instance, the system contains 21 equations and 17 unknown bytes. This is very close to the upper limit for an exhaustive key search, which is 16 bytes. One only needs to acquire 36 bytes of keystream to generate the equations. Therefore, the security of this cipher depends on the difficulty of solving this small system of equations. The third contribution is the proposal of an alternative method to measure diffusion in the linear transformation of Substitution-Permutation-Network (SPN) block ciphers. Currently, the branch number is widely used for this purpose. It is useful for estimating the possible success of differential and linear attacks on a particular SPN cipher. However, the measure does not give information on the number of input bits that are left unchanged by the transformation when producing the output bits. The new measure introduced in this thesis is intended to complement the current branch number technique. The measure is based on fixed points and simple linear relationships between the input and output words of the linear transformation. The measure represents the average fraction of input words to a linear diffusion transformation that are not effectively changed by the transformation. This measure is applied to the block ciphers AES, ARIA, Serpent and Present. It is shown that except for Serpent, the linear transformations used in the block ciphers examined do not behave as expected for a random linear transformation. The fourth contribution is the identification of linear paths in the nonlinear round function of the SMS4 block cipher. The SMS4 block cipher is used as a standard in the Chinese Wireless LAN Wired Authentication and Privacy Infrastructure (WAPI) and hence, the round function should exhibit a high level of nonlinearity. However, the findings in this thesis on the existence of linear relationships show that this is not the case. It is shown that in some exceptional cases, the first four rounds of SMS4 are effectively linear. In these cases, the effective number of rounds for SMS4 is reduced by four, from 32 to 28. The findings raise questions about the security provided by SMS4, and might provide clues on the existence of a flaw in the design of the cipher.
12
Carter, Gary Peter. "The design, analysis and categorization of block ciphers and their components." Thesis, Queensland University of Technology, 1999.
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13
Junior, Marcos Antonio Simplicio. "Algoritmos criptográficos para redes de sensores." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-30092008-182545/.
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É crescente a necessidade de prover segurança às informações trocadas nos mais diversos tipos de redes. No entanto, redes amplamente dependentes de dispositivos com recursos limitados (como sensores, tokens e smart cards) apresentam um desafio importante: a reduzida disponibilidade de memória, capacidade de processamento e (principalmente) energia dos mesmos dificulta a utilização de alguns dos principais algoritmos criptográficos considerados seguros atualmente. É neste contexto que se insere o presente documento, que não apenas apresenta uma pesquisa envolvendo projeto e análise de algoritmos criptográficos, mas também descreve um novo algoritmo simétrico denominado CURUPIRA. Esta cifra de bloco baseia-se na metodologia conhecida como Estratégia de Trilha Larga e foi projetada especialmente para ambientes onde existe escassez de recursos. O CURUPIRA possui estrutura involutiva, o que significa que os processos de encriptação e decriptação diferem apenas na seqüência da geração de chaves, dispensando a necessidade de algoritmos distintos para cada uma destas operações. Além disto, são propostas duas formas diferentes para seu algoritmo de geração de chaves, cada qual mais focada em segurança ou em desempenho. Entretanto, ambas as formas caracterizam-se pela possibilidade de computação das sub-chaves de round no momento de sua utilização, em qualquer ordem, garantindo uma operação com reduzido uso de memória RAM.The need for security is a great concern in any modern network. However, networks that are highly dependent of constrained devices (such as sensors, tokens and smart cards) impose a difficult challenge: their reduced availability of memory, processing power and (more importantly) energy hinders the deployment of many important cryptographic algorithms known to be secure. In this context, this document not only presents the research involving the design and analysis of cryptographic algorithms, but also proposes a new symmetric block cipher named CURUPIRA. The CURUPIRA follows the methodology known as theWide Trail Strategy and was specially developed having constrained platforms in mind. It displays an involutional structure, which means that the encryption and decryption processes differ only in the key schedule and, thus, there is no need to implement them separately. Also, two distinct scheduling algorithms are proposed, whose main focus are either on tight security or improved performance. In spite of this difference, both of them allow the keys to be computed on-the-fly, in any desired order, assuring a reduced consumption of RAM memory during their operation.
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Chaigneau, Colin. "Cryptanalyse des algorithmes de chiffrement symétrique." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV086/document.
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La sécurité des transmissions et du stockage des données est devenue un enjeu majeur de ces dernières années et la cryptologie, qui traite de la protection algorithmique de l'information, est un sujet de recherche extrêmement actif. Elle englobe la conception d'algorithmes cryptographiques, appelée cryptographie, et l'analyse de leur sécurité, appelée cryptanalyse.Dans cette thèse, nous nous concentrons uniquement sur la cryptanalyse, et en particulier celle des algorithmes de chiffrement symétrique, qui reposent sur le partage d'un même secret entre l'entité qui chiffre l'information et celle qui la déchiffre. Dans ce manuscrit, trois attaques contre des algorithmes de chiffrement symétriques sont présentées. Les deux premières portent sur deux candidats de l'actuelle compétition cryptographique CAESAR, les algorithmes AEZ et NORX, tandis que la dernière porte sur l'algorithme Kravatte, une instance de la construction Farfalle qui utilise la permutation de la fonction de hachage décrite dans le standard SHA-3. Les trois algorithmes étudiés présentent une stratégie de conception similaire, qui consiste à intégrer dans une construction nouvelle une primitive, i.e. une fonction cryptographique élémentaire, déjà existante ou directement inspirée de travaux précédents.La compétition CAESAR, qui a débuté en 2015, a pour but de définir un portefeuille d'algorithmes recommandés pour le chiffrement authentifié. Les deux candidats étudiés, AEZ et NORX, sont deux algorithmes qui ont atteint le troisième tour de cette compétition. Les deux attaques présentées ici ont contribué à l'effort de cryptanalyse nécessaire dans une telle compétition. Cet effort n'a, en l'occurrence, pas permis d'établir une confiance suffisante pour justifier la présence des algorithmes AEZ et NORX parmi les finalistes.AEZ est une construction reposant sur la primitive AES, dont l'un des principaux objectifs est d'offrir une résistance optimale à des scénarios d'attaque plus permissifs que ceux généralement considérés pour les algorithmes de chiffrement authentifié. Nous montrons ici que dans de tels scénarios il est possible, avec une probabilité anormalement élevée, de retrouver l'ensemble des secrets utilisés dans l'algorithme.NORX est un algorithme de chiffrement authentifié qui repose sur une variante de la construction dite en éponge employée par exemple dans la fonction de hachage Keccak. Sa permutation interne est inspirée de celles utilisées dans BLAKE et ChaCha. Nous montrons qu'il est possible d'exploiter une propriété structurelle de cette permutation afin de récupérer la clé secrète utilisée. Pour cela, nous tirons parti du choix des concepteurs de réduire les marges de sécurité dans le dimensionnement de la construction en éponge.Enfin, la dernière cryptanalyse remet en cause la robustesse de l'algorithme Kravatte, une fonction pseudo-aléatoire qui autorise des entrées et sorties de taille variable. Dérivée de la permutation Keccak-p de SHA-3 au moyen de la construction Farfalle, Kravatte est efficace et parallélisable. Ici, nous exploitons le faible degré algébrique de la permutation interne pour mettre au jour trois attaques par recouvrement de clé : une attaque différentielle d'ordre supérieur, une attaque algébrique "par le milieu" et une attaque inspirée de la cryptanalyse de certains algorithmes de chiffrement à flotNowadays, cryptology is heavily used to protect stored and transmitted data against malicious attacks, by means of security algorithms. Cryptology comprises cryptography, the design of these algorithms, and cryptanalysis, the analysis of their security.In this thesis, we focus on the cryptanalysis of symmetric encryption algorithms, that is cryptographic algorithms that rely on a secret value shared beforehand between two parties to ensure both encryption and decryption. We present three attacks against symmetric encryption algorithms. The first two cryptanalyses target two high profile candidates of the CAESAR cryptographic competition, the AEZ and NORX algorithms, while the last one targets the Kravatte algorithm, an instance of the Farfalle construction based on the Keccak permutation. Farfalle is multipurpose a pseudo-random function (PRF) developed by the same designers' team as the permutation Keccak used in the SHA-3 hash function.The CAESAR competition, that began in 2015, aims at selecting a portfolio of algorithms recommended for authenticated encryption. The two candidates analysed, AEZ and NORX, reached the third round of the CAESAR competition but were not selected to be part of the finalists. These two results contributed to the cryptanalysis effort required in such a competition. This effort did not establish enough confidence to justify that AEZ and NORX accede to the final round of the competition.AEZ is a construction based on the AES primitive, that aims at offering an optimal resistance against more permissive attack scenarios than those usually considered for authenticated encryption algorithms. We show here that one can recover all the secret material used in AEZ with an abnormal success probability.NORX is an authenticated encryption algorithm based on a variant of the so-called sponge construction used for instance in the SHA-3 hash function. The internal permutation is inspired from the one of BLAKE and ChaCha. We show that one can leverage a strong structural property of this permutation to recover the secret key, thanks to the designers' non-conservative choice of reducing the security margin in the sponge construction.Finally, the last cryptanalysis reconsiders the robustness of the Kravatte algorithm. Kravatte is an efficient and parallelizable PRF with input and output of variable length. In this analysis, we exploit the low algebraic degree of the permutation Keccak used in Kravatte to mount three key-recovery attacks targeting different parts of the construction: a higher order differential attack, an algebraic meet-in-the-middle attack and an attack based on a linear recurrence distinguisher
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Lallemand, Virginie. "Cryptanalyse de chiffrements symétriques." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066657/document.
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Les travaux réalisés dans cette thèse ont pour objet l'analyse de la sécurité de chiffrements à clef secrète. Plus précisément, nous y décrivons la cryptanalyse de plusieurs chiffrements par blocs et à flot ayant pour point commun d'avoir été conçus récemment pour répondre aux nouveaux enjeux de la cryptographie symétrique. Nous mettons en avant des attaques des versions complètes de cinq chiffrements, prouvant ainsi que ces primitives cryptographiques n'apportent pas la sécurité annoncée par leurs concepteurs.La première partie de cette thèse est dédiée à l'analyse de chiffrements par blocs avec des techniques de cryptanalyse différentielle. Nous montrons comment mener une attaque par différentielles tronquées sur la famille de chiffrements à bas coût KLEIN en exploitant la faible diffusions de sa fonction de tour. Ensuite, nous nous intéressons à Zorro et à Picaro, deux chiffrements conçus de sorte à être faciles à protéger contre les attaques par canaux auxiliaires, et montrons que les choix de conception guidés par cette contrainte ont engendré des faiblesses dans leurs propriétés différentielles, pouvant ensuite être exploitées dans des attaques.La seconde partie du manuscrit porte sur la cryptanalyse de chiffrements à flot. Nous y étudions Sprout et Flip, deux chiffrements aux structures innovantes visant respectivement à limiter la taille du circuit matériel nécessaire à l'implémentation et une bonne adaptation dans un schéma de FHEThe main subject of this thesis is the security analysis of symmetric key ciphers. Specifically, we study several recently proposed block and stream ciphers and prove that the level of security stated by their designers is overestimated. The ciphers we study were all designed in order to meet the needs of one of the new applications of symmetric cryptography, which include symmetric ciphers for very constrained environments.The first part of the thesis is dedicated to the analysis of block ciphers with techniques based on differential cryptanalysis. We start with the description of a truncated differential attack on the family of lightweight ciphers KLEIN. Next, we analyse two ciphers that were designed in such a way that they could be easily and effectively protected against side-channel attacks: Zorro and Picaro. We show that the design choices made by their designers lead to weak diffusion properties. We exploit these imperfections to devise a differential cryptanalysis of Zorro and a related key attack on Picaro.The second part of this thesis deals with stream ciphers and gives an analysis of two innovative designs: Sprout and Flip. Sprout was designed in order to limit its hardware area size and to suit very constrained environments, while Flip reaches efficient performances when used in FHE schemes. In both cases, we find flaws that lead to attacks of the particular set of parameters proposed for these ciphers
16
Lallemand, Virginie. "Cryptanalyse de chiffrements symétriques." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066657.
Full textAbstract:
Les travaux réalisés dans cette thèse ont pour objet l'analyse de la sécurité de chiffrements à clef secrète. Plus précisément, nous y décrivons la cryptanalyse de plusieurs chiffrements par blocs et à flot ayant pour point commun d'avoir été conçus récemment pour répondre aux nouveaux enjeux de la cryptographie symétrique. Nous mettons en avant des attaques des versions complètes de cinq chiffrements, prouvant ainsi que ces primitives cryptographiques n'apportent pas la sécurité annoncée par leurs concepteurs.La première partie de cette thèse est dédiée à l'analyse de chiffrements par blocs avec des techniques de cryptanalyse différentielle. Nous montrons comment mener une attaque par différentielles tronquées sur la famille de chiffrements à bas coût KLEIN en exploitant la faible diffusions de sa fonction de tour. Ensuite, nous nous intéressons à Zorro et à Picaro, deux chiffrements conçus de sorte à être faciles à protéger contre les attaques par canaux auxiliaires, et montrons que les choix de conception guidés par cette contrainte ont engendré des faiblesses dans leurs propriétés différentielles, pouvant ensuite être exploitées dans des attaques.La seconde partie du manuscrit porte sur la cryptanalyse de chiffrements à flot. Nous y étudions Sprout et Flip, deux chiffrements aux structures innovantes visant respectivement à limiter la taille du circuit matériel nécessaire à l'implémentation et une bonne adaptation dans un schéma de FHEThe main subject of this thesis is the security analysis of symmetric key ciphers. Specifically, we study several recently proposed block and stream ciphers and prove that the level of security stated by their designers is overestimated. The ciphers we study were all designed in order to meet the needs of one of the new applications of symmetric cryptography, which include symmetric ciphers for very constrained environments.The first part of the thesis is dedicated to the analysis of block ciphers with techniques based on differential cryptanalysis. We start with the description of a truncated differential attack on the family of lightweight ciphers KLEIN. Next, we analyse two ciphers that were designed in such a way that they could be easily and effectively protected against side-channel attacks: Zorro and Picaro. We show that the design choices made by their designers lead to weak diffusion properties. We exploit these imperfections to devise a differential cryptanalysis of Zorro and a related key attack on Picaro.The second part of this thesis deals with stream ciphers and gives an analysis of two innovative designs: Sprout and Flip. Sprout was designed in order to limit its hardware area size and to suit very constrained environments, while Flip reaches efficient performances when used in FHE schemes. In both cases, we find flaws that lead to attacks of the particular set of parameters proposed for these ciphers
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Madhavarapu, Venkata Praveen Kumar. "A Novel Three Phase Symmetric Cipher Technique." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2031.
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Confusion and Diffusion are two properties of a secure cipher, identified by Claude Shannon. Confusion refers to making the relationship between the ciphertext and the symmetric key as complex and involved as possible. We try to achieve more confusion by creating a ciphertext of different length for a given plaintext when key is changed. As per our knowledge, all the existing symmetric encryption techniques will generate cipher text of same length for a given plaintext with different keys. The technique we are implementing here, will create ciphertext with different length for a given plaintext if we change the appropriate values in the key. This symmetric encryption technique will also possibly make the recovery of key very hard for the attacker.
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Aghaee, Saeed. "Random Stream Cipher." Thesis, Växjö University, School of Mathematics and Systems Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1511.
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Stream ciphers are counted as an important part of symmetric encryption method. Their basic idea comes from One-Time-Pad cipher using XOR operator on the plain text and the key to generate the cipher. The present work brings a new idea in symmetric encryption method, which inherits stream key generation idea from synchronous stream cipher and uses division instead of xoring. The Usage of division to combine the plain text with stream key gives numerous abilities to this method that the most important one is using random factors to produce the ciphers.
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Jeddi, Zahra. "A Lightweight Authenticated Symmetric Encryption Cipher for RFID Systems." Thesis, University of Louisiana at Lafayette, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3687692.
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Radio Frequency Identification, RFID, is a type of automatic identification system which has gained popularity in recent years for being fast and reliable in keeping track of individual objects. Due to limited available resources in RFID tags, providing privacy and security for RFID systems is one of the important challenges nowadays. In this dissertation, a lightweight symmetric encryption algorithm called RBS, Redundant Bit Security, is presented which is suitable for resource constrained applications like RFID systems. Confidentiality of the plaintext in this algorithm is achieved through inserting some redundant bits inside the plaintext bits where the location of redundant bits inside the ciphertext is the secret key shared between sender and receiver. Besides confidentiality, these redundant bits are calculated in such a way that they provide authentication and integrity as well. The security of the algorithm is analyzed against some well-known attacks such as known plaintext, known ciphertext, chosen plaintext, and differential attacks. Experimental and simulation results confirm that RBS implementation requires less power and area overhead compared to other known symmetric algorithms proposed for RFID systems, especially when the authentication is essential like in harsh environments.
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Boukerrou, Hamid. "Design of New Finite State Dynamical Systems Admitting a Matrix Representation : Application to Cryptography." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0069.
Full textAbstract:
L'essor considérable des technologies de l'information et de la communication, dans le contexte actuel de la révolution numérique et de l'Internet des Objets, nécessite de renforcer la sécurité des données et des systèmes. Dans ce contexte, la cryptographie joue un rôle important. Les machines à état fini (FSM pour Finite State Machines en anglais) sont des briques élémentaires couramment utilisées en cryptographie symétrique, en particulier pour le chiffrement par flot (Stream Ciphering en anglais). Ces objets mathématiques sont également usuels en automatique pour décrire des systèmes discrets. Ces modèles sont au cœur du travail qui a été conduit. Depuis le début des années 90, la littérature fait état d'architectures variées pour construire des chiffreurs symétriques de type auto-synchronisants (SSSC pour Self-Synchronizing Stream Ciphers en anglais). Mais toutes les propositions de chiffreurs ont révélé des failles justifiant la nécessité de nouvelles architectures. Dans cette thèse, de nouvelles primitives cryptographiques auto-synchronisantes, basée sur des machines à état fini de type Linear Parameter Varying (LPV) plats, ont été proposées. La motivation de cette classe de systèmes a été soulignée du point de vue de la sécurité et des performances de synchronisation. A l'issue d'une analyse d'une architecture de type mono-entrée, mono-sortie (Single Input Single Output, SISO), la justification d'extensions à des structures multi-entrées, multi-sorties (Multi Inputs Multi Ouputs) avec délai de synchronisation soit déterministe, soit statistique, a été donnée. Principalement deux notions de la théorie du contrôle ont été développées pour effectuer la synthèse des automates : la platitude et l'analyse structurelle. Des preuves de concepts illustrent les bénéfices des ces nouvelles architectures vis-à-vis de l'état de l'artThe considerable growth of information and communication technologies, in the current context of the digital revolution and the Internet of Things, requires the strengthening of data and system security. In this context, cryptography plays an important role.Finite State Machines (FSM) are elementary building blocks commonly used in symmetric cryptography, in particular for Stream Ciphering. These mathematical objects are also commonly used in automation to describe discrete systems. These models are at the heart of the work that has been conducted.Since the beginning of the 90's, the literature has reported various architectures for building symmetric self-synchronizing stream ciphers (SSSC). But all the proposed ciphers have revealed flaws justifying the need for new architectures. In this thesis, new self-synchronizing cryptographic primitives, based on flat Linear Parameter Varying (LPV) finite state machines, have been proposed. The motivation of this class of systems was underlined from the point of view of security and synchronization performances. After an analysis of a Single Input Single Output (SISO) architecture, the justification for extensions to Multi Inputs Multi Ouputs structures with either deterministic or statistical synchronization delay has been given.Mainly two notions of control theory have been developed to perform the synthesis of automata: flatness and structural analysis. Proofs of concepts illustrate the benefits of these new architectures with respect to the state of the art
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Alshahrani, Ali Mohammed S. "Tesseract : a 4D symmetric block cipher cryptography solution for real-time applications." Thesis, University of Essex, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.701375.
Full textAbstract:
Security issues are a major concern, especially with real-time applications that are very time- sensitive because of file size. Cryptography is one of the main techniques used to provide the necessary data security. As is well known, the concept of the cryptography is to convert the plaintext into an unreadable version on the sender side by using an encryption key. At the receiver side, the ciphertext is returned into its original situation. Of particular relevance is key space viz. the number of possible keys that can be used to generate the key from the keys container. This is very important against brute force attacks. Many algorithms have been published; however, they feature limitations pertaining to security level, encryption key size, performance speed or incompatibility with the real-time applications. In this thesis, innovative 4D tesseract-based solutions (T-key) are suggested, implemented, tested and shown to overcome the drawbacks of most existing algorithms. They are based on a symmetric block cipher technique and have a large key-space (e.g. 384-bit). In-this thesis, three key size are suggested as examples, which are tested and evaluated: T-{O,l}128, T-{O,1}256 and T-{O,1}512. Moreover, four lightweight coding rounds are applied to create these keys from the 4D tesseract key containers. The execution speed of the T-key was compared with the AES cipher, and the results indicated that the first two encryption key sizes suggested here are faster than the first two encryption keys of AES. Furthermore, the security evaluations carried out on the suggested algorithm showed full resistance to statistical attacks and a comprehensive pass of correlation coefficient tests.
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Di, Binbin. "Analysis of one-pass block cipher based authenticated encryption schemes." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/87437/1/Binbin_Di_Thesis.pdf.
Full textAbstract:
This project analyses and evaluates the integrity assurance mechanisms used in four Authenticated Encryption schemes based on symmetric block ciphers. These schemes are all cross chaining block cipher modes that claim to provide both confidentiality and integrity assurance simultaneously, in one pass over the data. The investigations include assessing the validity of an existing forgery attack on certain schemes, applying the attack approach to other schemes and implementing the attacks to verify claimed probabilities of successful forgeries. For these schemes, the theoretical basis of the attack was developed, the attack algorithm implemented and computer simulations performed for experimental verification.
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Cogliati, Benoît-Michel. "Le schéma d'Even-Mansour paramétrable : preuves de sécurité à l'aide de la technique des coefficients H." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV064/document.
Full textAbstract:
Les algorithmes de chiffrement par blocs paramétrables constituent une généralisation des algorithmes de chiffrement par blocs classiques qui, en plus d'une clé et d'un message à chiffrer ou déchiffrer, admettent un paramètre additionnel, nommé tweak en anglais. Le rôle de ce paramètre additionnel est d'apporter une variabilité à l'algorithme de chiffrement, sans qu'il soit nécessaire de changer la clé ou de garder le tweak secret. Ce dernier doit également pouvoir être contrôlé par l'adversaire sans dégradation de la sécurité. Dans cette thèse nous nous intéressons à une classe particulière d'algorithmes de chiffrement par blocs, les algorithmes de chiffrement par blocs à clé alternée. Plusprécisément, nous étudions la sécurité du schéma d'Even-Mansour, qui constitue une abstraction de la structure de ces algorithmes dans le modèle de la permutation aléatoire, et cherchons à rendre ce schéma paramétrable tout en conservant de fortes garanties de sécurité. À cette fin, nous introduisons une nouvelle construction générique, baptiséeTEM, qui remplace les clés de tours de la construction d'Even-Mansour par une valeur qui dépend de la clé et du tweak, et en étudions la sécurité dans deux cas : lorsque le mixage de la clé et du tweak est linéaire ou lorsqu'il est très non-linéaire. Nos preuves de sécurité utilisent la technique des coefficients H, introduite par Jacques Patarin danssa thèse de doctorat, qui permet de transformer des problèmes cryptographiques en problèmes combinatoires sur des groupes finisTweakable block ciphers are a generalization of classical block ciphers which, in addition to a key and a plaintext or a ciphertext, take an additionnal parameter called a tweak. The goal of this new parameter is to bring variability to the block cipher without needing to change the key or to keep the tweak secret. The tweak should also be adversariallycontrollable without sacrificing security. In this thesis we study a particular class of block ciphers, namely key-alternating ciphers. More precisely, we study the security of the Even-Mansour scheme, which is an abstraction of these ciphers in the random permutation model, and seek to bring tweakability to this scheme while keeping strong security guarantees. To this end, we introduce a new generic construction, dubbed TEM, which replaces the round keys from the Even-Mansour construction by a value depending on both the key and the tweak, and study its security in two cases: when the tweak and key mixing is linear or highly non-linear. Our security proofs rely on the H-coefficients technique, a technique introduced by Jacques Patarin in his PhD thesis which transforms cryptographic problems into combinatorial problems in finite groups
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Flórez, Gutiérrez Antonio. "Improved Techniques in the Cryptanalysis of Symmetric Primitives." Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS281.
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Dans cette thèse, on propose des améliorations qui peuvent être appliquées à plusieurs techniques de cryptanalyse de primitives symétriques. On dédie une attention spéciale à la cryptanalyse linéaire, pour laquelle une technique basée sur la transformée de Walsh rapide était déjà connue (Collard et al., ICISC 2007). On introduit une version généralisée de cette attaque, qui permet de l'appliquer pour la récupération de clé considerant plusieurs tours, ainsi que le réduction de la complexité du problème en utilisant par example des informations provénantes du key-schedule. On propose aussi une technique générale pour accélérer les attaques par récupération de clé qui est basée sur la représentation des boîtes S en tant que arbres binaires. Finalement, on montre comment on a obtenu une approximation linéaire sur la version complète de la permutation Gimli en utilisant l'optimisation par mixed-integer linear programming (MILP)This thesis proposes improvements which can be applied to several techniques for the cryptanalysis of symmetric primitives. Special attention is given to linear cryptanalysis, for which a technique based on the fast Walsh transform was already known (Collard et al., ICISIC 2007). We introduce a generalised version of this attack, which allows us to apply it on key recovery attacks over multiple rounds, as well as to reduce the complexity of the problem using information extracted, for example, from the key schedule. We also propose a general technique for speeding key recovery attacks up which is based on the representation of Sboxes as binary decision trees. Finally, we showcase the construction of a linear approximation of the full version of the Gimli permutation using mixed-integer linear programming (MILP) optimisation
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ALMashrafi, Mufeed Juma. "Analysis of stream cipher based authenticated encryption schemes." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/60916/1/Mufeed_ALMashrafi_Thesis.pdf.
Full textAbstract:
Authenticated Encryption (AE) is the cryptographic process of providing simultaneous confidentiality and integrity protection to messages. This approach is more efficient than applying a two-step process of providing confidentiality for a message by encrypting the message, and in a separate pass providing integrity protection by generating a Message Authentication Code (MAC). AE using symmetric ciphers can be provided by either stream ciphers with built in authentication mechanisms or block ciphers using appropriate modes of operation.
However, stream ciphers have the potential for higher performance and smaller footprint in hardware and/or software than block ciphers. This property makes stream ciphers suitable for resource constrained environments, where storage and computational power are limited. There have been several recent stream cipher proposals that claim to provide AE. These ciphers can be analysed using existing techniques that consider confidentiality or integrity separately; however currently there is no existing framework for the analysis of AE stream ciphers that analyses these two properties simultaneously. This thesis introduces a novel framework for the analysis of AE using stream cipher algorithms.
This thesis analyzes the mechanisms for providing confidentiality and for providing integrity in AE algorithms using stream ciphers. There is a greater emphasis on the analysis of the integrity mechanisms, as there is little in the public literature on this, in the context of authenticated encryption. The thesis has four main contributions as follows.
The first contribution is the design of a framework that can be used to classify AE stream ciphers based on three characteristics. The first classification applies Bellare and Namprempre's work on the the order in which encryption and authentication processes take place. The second classification is based on the method used for accumulating the input message (either directly or indirectly) into the into the internal states of the cipher to generate a MAC. The third classification is based on whether the sequence that is used to provide encryption and authentication is generated using a single key and initial vector, or two keys and two initial vectors.
The second contribution is the application of an existing algebraic method to analyse the confidentiality algorithms of two AE stream ciphers; namely SSS and ZUC. The algebraic method is based on considering the nonlinear filter (NLF) of these ciphers as a combiner with memory. This method enables us to construct equations for the NLF that relate the (inputs, outputs and memory of the combiner) to the output keystream. We show that both of these ciphers are secure from this type of algebraic attack. We conclude that using a keydependent SBox in the NLF twice, and using two different SBoxes in the NLF of ZUC, prevents this type of algebraic attack.
The third contribution is a new general matrix based model for MAC generation where the input message is injected directly into the internal state. This model describes the accumulation process when the input message is injected directly into the internal state of a nonlinear filter generator. We show that three recently proposed AE stream ciphers can be considered as instances of this model; namely SSS, NLSv2 and SOBER-128. Our model is more general than a previous investigations into direct injection. Possible forgery attacks against this model are investigated. It is shown that using a nonlinear filter in the accumulation process of the input message when either the input message or the initial states of the register is unknown prevents forgery attacks based on collisions.
The last contribution is a new general matrix based model for MAC generation where the input message is injected indirectly into the internal state. This model uses the input message as a controller to accumulate a keystream sequence into an accumulation register. We show that three current AE stream ciphers can be considered as instances of this model; namely ZUC, Grain-128a and Sfinks.
We establish the conditions under which the model is susceptible to forgery and side-channel attacks.
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Juras, Stanislav. "Autentizace pomocí smartkaret." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218350.
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The master’s thesis outlines the problem of authentication. It describes authentication factors like ownership, knowledge and inherent. There are described properties of each of that. Authentication based on ownership focuses on authenticators - the smartcards. The thesis also describes different types of smartcards (contact, contactless and hybrid smartcards) and refers to their basic properties. Emphasis is placed on the description of contact and contactless smartcard, specifically focusing on .NET smartcards. It describes their internal components such as memory (RAM, ROM, EEPROM), crypto processor etc. Smartcards are also examined in terms of support for cryptographic primitives. The thesis also introduces the cryptographic methods and principles describing symmetric and asymmetric ciphers. Symmetric ciphers are divided in to stream and block ciphers. There is description of asymmetric cipher, digital signature etc. This work also touches on the fundamental principles required for safe programming. Part of this work is also practical implementation (programs). Practical part aims to implement the communication between the user and AC (Access Control) AASR system. The first suite of applications provides encrypted communication between the PC and smartcards. These applications should create on smartcard services that will be able to perform operations on the client side, which are necessary to authenticate in the AASR system. The paper also presents algorithms for working with big numbers - addition, subtraction, multiplication, and Montgomery's algorithm for multiplication. The second application implements the functionality of AC components (Access Control). This functionality is for example – authenticate received token, digital signature authentication, generating random numbers, logging etc.
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Karpman, Pierre. "Analyse de primitives symétriques." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX095/document.
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Cette thèse a pour objet d'étude les algorithmes de chiffrement par blocet les fonctions de hachage cryptograpiques, qui sont deux primitives essentielles de la cryptographie dite «symétrique».Dans une première partie, nous étudions des éléments utiles pour la conception de chiffres par bloc: tout d'abord des matrices de diffusion de grande dimension issues de codes correcteurs géométriques, puis une boîte de substitution offrant une bonne diffusion. Dans le second cas, nous montrons aussi comment utiliser cet élément pour construire un chiffre compact et efficace sur petits processeurs.Dans une seconde partie, nous nous intéressons à des attaques en collision à initialisation libre sur la fonction de hachage SHA-1. Nous montrons comment les attaques classiques sur cette fonction peuvent être rendues plus efficaces en exploitant la liberté supplémentaire offerte par ce modèle. Ceci nous permet en particulier de calculer explicitement des collisions pour la fonction de compression de SHA-1 non réduiteThis thesis is about block ciphers and cryptographic hash functions, which are two essential primitives of symmetric-key cryptography. In the first part of this manuscript, we study useful building blocks for block cipher design. We first consider large diffusion matrices builtfrom algebraic-geometry codes, and then construct a small S-box with good diffusion. In the second case, we show how the S-box can be used to define a compact and efficient block cipher targetting small processors. In the second part, we focus on the SHA-1 hash function, for which we develop a free start collision attack. We show how classical collision attacks can be made more efficient by exploiting the additional freedom provided by the model. This allows us in particular to compute explicit collisions for the full compression function of SHA-1
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Rotella, Yann. "Mathématiques discrètes appliquées à la cryptographie symétrique." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS092/document.
Full textAbstract:
Dans cette thèse, nous étudions la sécurité de primitives cryptographiques. Ces systèmes sont fondés sur des transformations utilisant des objets mathématiques représentés de multiples manières. Nous utilisons alors certaines structures inhérentes à leurs composantes, et jusqu'alors non prises en compte, pour mettre en évidence de nouvelles vulnérabilités. Par l'exploitation de diverses représentations, nous avons ainsi cryptanalysé des chiffrements authentifiés de la compétition CAESAR, des chiffrements à flot spécifiques et des constructions génériques. Nous avons donné des critères de conception en vue de la standardisation par le NIST de chiffrements à bas coût. Dans le cas des chiffrements à flot, nous avons défini de nouveaux critères cryptographiques plus pertinents que les critères usuels. Plus précisément, nous analysons la sécurité des chiffrements par bloc légers au regard des récentes attaques par invariant, et nous montrons comment les éviter par un choix approprié de la couche linéaire de diffusion et des constantes de tour. Nous proposons une nouvelle cryptanalyse des registres filtrés, grâce à la décomposition des éléments dans les sous-groupes multiplicatifs du corps fini à 2^n éléments. L'analyse du chiffrement FLIP, mais aussi du générateur pseudo-aléatoire de Goldreich a mis en évidence des faiblesses exploitables dans des attaques de type ``supposer et déterminer'', qui nécessitent la prise en compte de nouveaux critères sur les fonctions booléennes utilisées dans ce contexte. Enfin, nous cryptanalysons une version simplifiée du chiffrement authentifié Ketje en utilisant plusieurs techniques, permettant ainsi d'affiner l'évaluation de sa sécuritéIn this thesis, we study the security of symmetric cryptographic primitives. These systems are based on transformations relying on mathematical objects that can be represented in multiple ways. We then exploit different induced structures to highlight new vulnerabilities. By exploiting various representations, we cryptanalyzed some schemes submitted to the CAESAR competition, and also some dedicated and generic stream ciphers. We exhibited design criteria for lightweight block ciphers in view of the NIST standardization process and in the case of stream ciphers we defined new cryptographic criteria more relevant than the usual ones. More precisely, we study the security of lightweight block ciphers with respect to the recent invariant attacks, and we show how to avoid them with an appropriate choice of the linear layer and the round constants. We propose a new cryptanalysis of the filtered registers, by decomposing elements in the multiplicative subgroups of the finite field with 2^n elements. The analysis of the FLIP cipher, but also of the Goldreich pseudo-random generator, revealed weaknesses that are exploitable in ``guess and determine'' attacks. This leads to new criteria on the Boolean functions used in this context. Finally, we cryptanalyze a weaker version of the authenticated encryption scheme Ketje using several techniques, in order to refine the security evaluation of this cipher
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Rotella, Yann. "Mathématiques discrètes appliquées à la cryptographie symétrique." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS092.
Full textAbstract:
Dans cette thèse, nous étudions la sécurité de primitives cryptographiques. Ces systèmes sont fondés sur des transformations utilisant des objets mathématiques représentés de multiples manières. Nous utilisons alors certaines structures inhérentes à leurs composantes, et jusqu'alors non prises en compte, pour mettre en évidence de nouvelles vulnérabilités. Par l'exploitation de diverses représentations, nous avons ainsi cryptanalysé des chiffrements authentifiés de la compétition CAESAR, des chiffrements à flot spécifiques et des constructions génériques. Nous avons donné des critères de conception en vue de la standardisation par le NIST de chiffrements à bas coût. Dans le cas des chiffrements à flot, nous avons défini de nouveaux critères cryptographiques plus pertinents que les critères usuels. Plus précisément, nous analysons la sécurité des chiffrements par bloc légers au regard des récentes attaques par invariant, et nous montrons comment les éviter par un choix approprié de la couche linéaire de diffusion et des constantes de tour. Nous proposons une nouvelle cryptanalyse des registres filtrés, grâce à la décomposition des éléments dans les sous-groupes multiplicatifs du corps fini à 2^n éléments. L'analyse du chiffrement FLIP, mais aussi du générateur pseudo-aléatoire de Goldreich a mis en évidence des faiblesses exploitables dans des attaques de type ``supposer et déterminer'', qui nécessitent la prise en compte de nouveaux critères sur les fonctions booléennes utilisées dans ce contexte. Enfin, nous cryptanalysons une version simplifiée du chiffrement authentifié Ketje en utilisant plusieurs techniques, permettant ainsi d'affiner l'évaluation de sa sécuritéIn this thesis, we study the security of symmetric cryptographic primitives. These systems are based on transformations relying on mathematical objects that can be represented in multiple ways. We then exploit different induced structures to highlight new vulnerabilities. By exploiting various representations, we cryptanalyzed some schemes submitted to the CAESAR competition, and also some dedicated and generic stream ciphers. We exhibited design criteria for lightweight block ciphers in view of the NIST standardization process and in the case of stream ciphers we defined new cryptographic criteria more relevant than the usual ones. More precisely, we study the security of lightweight block ciphers with respect to the recent invariant attacks, and we show how to avoid them with an appropriate choice of the linear layer and the round constants. We propose a new cryptanalysis of the filtered registers, by decomposing elements in the multiplicative subgroups of the finite field with 2^n elements. The analysis of the FLIP cipher, but also of the Goldreich pseudo-random generator, revealed weaknesses that are exploitable in ``guess and determine'' attacks. This leads to new criteria on the Boolean functions used in this context. Finally, we cryptanalyze a weaker version of the authenticated encryption scheme Ketje using several techniques, in order to refine the security evaluation of this cipher
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Škoda, Martin. "Implementace symetrické blokové šifry AES na moderních procesorech." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220616.
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The main aim of master's thesis is usage of new instructions from instruction set called Intel® Advanced Encryption Standard New Instructions (AES-NI), which is available on processors with code name Westmere and newer. In theoretical part, there are described symmetric block ciphers and their operational modes. Cipher AES is described in details, especially used block transformations, key expansion and equivalent inverse cipher. Next topic is description of instructions of AES-NI instruction set – their function is explained using pseudo codes of instructions and there are examples of their usage in code. Further in work, dynamic-link library is created, which implements cipher AES with key sizes 128, 192 and 256 bites and implements operational modes described in theoretical part. Library functions are called from Matlab by scripts and their functionality is proved by checking test vectors values, which are provided in publications of National Institute of Standards and Technology.
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Thuillet, Céline. "Implantations cryptographiques sécurisées et outils d’aide à la validation des contremesures contre les attaques par canaux cachés." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14508/document.
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Depuis plusieurs années, les composants dédiés à la sécurité comme les cartes à puce sont soumises à des attaques dites par canaux cachés. Ces attaques permettent d'exhiber les secrets en analysant des caractéristiques physiques comme la consommation du composant ou encore son temps d'exécution. Dans le cadre de cette thèse, deux contremesures ont été réalisées et appliquées à l'AES (algorithme de chiffrement symétrique). De plus, afin d'aider les développements futurs des contremesures et la validation de celles-ci, un simulateur a été développé. Il permet de réaliser des attaques grâce à un modèle de consommation défini dans les phases amont de développement. Enfin, j'ai pu participer aux groupes de travail qui ont proposé Shabal à la compétition SHA-3, qui vise à définir un nouveau standard pour les fonctions de hachage. Des implantations matérielles ont été réalisées par la suiteFor several years, the security components such as smart cards are subject to side channel attacks. These attacks allow to exhibit secrets by analyzing the physical characteristics such as power consumption or execution time. As part of this thesis, two countermeasures were carried out and applied to the AES (symmetric cipher). In addition, to help future development of countermeasures and their validation, a simulator was developed. It realizes attacks using a power consumption model defined in the early phases of development. Finally, I participated in working groups that have proposed Shabal to SHA-3 competition, which aims to define a new standard for hash functions. Hardware implementations have been made thereafter
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Forman, Tomáš. "Portál pro podporu výuky kryptografie." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218332.
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The main goal of this master's thesis is building of web portal for presentation basic cryptography algorithms. Those algorithms would be explained in the theoretical page in the first place. After that, they would be demonstrated by scripts. One part of this project is designing simplified theoretical element for basic impletion portal of information. Next part is creating web portal by one of the free available CMS´s systems. Programming language JAVA would be used as an instrument for creating demonstration scripts. For creating animations will be used the Flash animation tool. Target of formed web portal is creating community of expert public. It would make new articles, scripts and knowledge. This way, the portal would be kept current. The section which would include failure the most widely used algorithms and instructions how to eliminate it will be part of portal.
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El, Amrani Nora. "Codes additifs et matrices MDS pour la cryptographie." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0034/document.
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Cette thèse porte sur les liens entre les codes correcteurs d'erreurs et les matrices de diffusion linéaires utilisées en cryptographie symétrique. L'objectif est d'étudier les constructions possibles de codes MDS additifs définis sur le groupe (Fm2, +) des m-uplets binaires et de minimiser le coût de l'implémentation matérielle ou logicielles de ces matrices de diffusion. Cette thèse commence par l'étude des codes définis sur un anneau de polynômes du type F[x]/f(x), qui généralisent les codes quasi-cycliques. Elle se poursuit par l'étude des codes additifs systématiques définis sur (Fm2, +) et leur lien avec la diffusion linéaire en cryptographie symétrique. Un point important de la thèse est l'introduction de codes à coefficient dans l'anneau des endomorphismes de Fm2. Le lien entre les codes qui sont des sous-modules à gauche et les codes additifs est mis en évidence. La dernière partie porte sur l'étude et la construction de matrices de diffusion MDS ayant de bonnes propriétés pour la cryptographie, à savoir les matrices circulantes, les matrices dyadiques, ainsi que les matrices ayant des représentations creuses minimisant leur implémentationThis PhD focuses on the links between error correcting codes and diffusion matrices used in cryptography symmetric. The goal is to study the possible construction of additives MDS codes defined over the group (Fm2, +) of binary m-tuples and minimize cost of hardware or software implementation of these diffusion matrices. This thesis begins with the study of codes defined over the polynomial ring F[x]/f(x), these codes are a generalization of quasi-cyclic codes, and continues with the study of additive systematic codes over (Fm2, +) and there relation with linear diffusion on symmetric cryptography. An important point of this thesis is the introduction of codes with coefficients in the ring of endomorphisms of Fm2. The link between codes which are a left-submodules and additive codes have been identified. The last part focuses on the study and construction of efficient diffusion MDS matrices for the cryptographic applications, namely the circulantes matrices, dyadic matrices, and matrices with hollow representation, in ordre to minimize their implementations
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Coggia, Daniel. "Techniques de cryptanalyse dédiées au chiffrement à bas coût." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS217.
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Cette thèse contribue à l’effort de cryptanalyse de primitives symétriques comme les chiffrements par bloc ou les générateurs pseudo-aléatoires. Elle étudie en particulier une famille de distingueurs fondés sur la propagation de sous-espaces vectoriels différentiels dans les chiffrements par bloc de construction SPN. Cette thèse propose également des méthodes permettant aux cryptographes de modéliser un problème de cryptanalyse de primitive symétrique en problème MILP (Mixed-Integer Linear Programming), afin d’exploiter certains logiciels solutionneurs de problèmes MILP très performants. Enfin, elle présente des techniques d’analyse algébrique des primitives symétriques, fondées sur le calcul d’une partie de leur forme algébrique normale, et utiles dans les attaques de type cubeThis thesis contributes to the cryptanalysis effort needed to trust symmetric-key primitives like block-ciphers or pseudorandom generators. In particular, it studies a family of distinguishers based on subspace trails against SPN ciphers. This thesis also provides methods for modeling frequent cryptanalysis problems into MILP (Mixed-Integer Linear Programming) problems to allow cryptographers to benefit from the existence of very efficient MILP solvers. Finally, it presents techniques to analyze algebraic properties of symmetric-key primitives which could be useful to mount cube attacks
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Fujdiak, Radek. "Analýza a optimalizace datové komunikace pro telemetrické systémy v energetice." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-358408.
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Telemetry system, Optimisation, Sensoric networks, Smart Grid, Internet of Things, Sensors, Information security, Cryptography, Cryptography algorithms, Cryptosystem, Confidentiality, Integrity, Authentication, Data freshness, Non-Repudiation.
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Sahu, Harish Kumar. "Cryptanalysis of symmetric ciphers using robdds and smt solvers." Thesis, 2018. http://localhost:8080/xmlui/handle/12345678/7699.
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Čanda, Valér [Verfasser]. "Scalable symmetric block ciphers based on group bases / von Valér Čanda." 2001. http://d-nb.info/962789755/34.
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Barakat, Mohamed L. "Hardware Realization of Chaos Based Symmetric Image Encryption." Thesis, 2012. http://hdl.handle.net/10754/234953.
Full textAbstract:
This thesis presents a novel work on hardware realization of symmetric image encryption utilizing chaos based continuous systems as pseudo random number generators. Digital implementation of chaotic systems results in serious degradations in the dynamics of the system. Such defects are illuminated through a new technique of generalized post proceeding with very low hardware cost. The thesis further discusses two encryption algorithms designed and implemented as a block cipher and a stream cipher. The security of both systems is thoroughly analyzed and the performance is compared with other reported systems showing a superior results. Both systems are realized on Xilinx Vetrix-4 FPGA with a hardware and throughput performance surpassing known encryption systems.
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Піх, Василь Володимирович, and Vasyl Pikh. "Оцінка ефективності алгоритмів блоково-симетричного шифрування на основі використання міні-версій." Master's thesis, 2020. http://elartu.tntu.edu.ua/handle/lib/33440.
Full textAbstract:
Роботу виконано на кафедрі кібербезпеки Тернопільського національного технічного університету імені Івана Пулюя Міністерства освіти і науки України
Керівник роботи: д.т.н., проф. кафедри кібербезпеки
Карпінський Микола Петрович,
Тернопільський національний технічний університет імені Івана Пулюя
Рецензент: кандидат технічних наук, асистент кафедри комп’ютерних наук
Никитюк Вячеслав Вячеславович,
Тернопільський національний технічний університет імені Івана ПулюяДана магістерська кваліфікаційна робота присвячена дослідженню методів підвищення ефективності використання міні-версій БСШ для оцінки криптостійкості повних шифрів. Об’єктом дослідження є процес забезпечення адекватності використання міні-версій щодо оцінки криптостійкості повних шифрів. Предметом дослідження є оцінка ефективності алгоритмів блоково-симетричного шифрування на основі використання міні-версій. Алгоритми реалізовані на основі програмного забезпечення, розробленого в середовищі Microsoft Visual Studio 2013 мовою С# та С++. При дослідженні алгоритмів конкурсантів використовувалася оцінка трьох показників: стійкості алгоритму до відомих криптоаналітичних атак, продуктивність програмної реалізації алгоритму на сучасних персональних комп’ютерах і “статистична безпека” (формування унікальних псевдовипадкових послідовностей). У результаті проведений порівняльний аналіз міні-версій блочних симетричних шифрів України, та оцінено адекватність їх використання. Методами розробки обрано: При аналізі методів і алгоритмів симетричної криптографії використовуються міні-версії шифрів –конкурсантів на алгоритм симетричного шифрування в Україні. При досліджені рівня їх стійкості використовуються основні положення теорій захисту та криптоаналізу, а саме методи лінійного та диференціального аналізу. При дослідженні стійкості алгоритму були використані методи теорії ймовірності та математичної статистики. У результаті роботи проведено дослідження можливості використання міні-версій алгоритмів традиційного шифрування щодо отримання їх властивостей повних шифрів за рахунок оцінки стійкості до методів лінійного та диференційного аналізу
This master's thesis is devoted to the study of methods to improve the efficiency of using mini-versions of block symmetric ciphers (BSС) to assess the cryptographic strength of complete ciphers. The object of the study is the process of ensuring the adequacy of the use of mini-versions in assessing the cryptographic strength of complete ciphers. The subject of the study is to evaluate the effectiveness of block-symmetric encryption algorithms based on the use of mini-versions. The algorithms are implemented on the basis of software developed in Microsoft Visual Studio 2013 in C # and C ++. In the study of the algorithms of the contestants used the assessment of three indicators: the resistance of the algorithm to known cryptanalytic attacks, the performance of software implementation of the algorithm on modern personal computers and “statistical security” (formation of unique pseudo-random sequences). As a result, a comparative analysis of mini-versions of block symmetric ciphers of Ukraine was conducted, and the adequacy of their use was assessed. Development methods selected: In the analysis of methods and algorithms of symmetric cryptography, mini-versions of ciphers are used – a competition for the symmetric encryption algorithm in Ukraine. In studying the level of their stability, the main provisions of the theories of protection and cryptanalysis are used, namely the methods of linear and differential analysis. Methods of probability theory and mathematical statistics were used to study the stability of the algorithm. As a result, the possibility of using mini-versions of traditional encryption algorithms to obtain their properties of complete ciphers by assessing the resistance to the methods of linear and differential analysis.
ВСТУП ...6 РОЗДІЛ 1 АНАЛІЗ МЕТОДІВ ОЦІНКИ ЕФЕКТИВНОСТІ БЛОКОВО-СИМЕТРИЧНИХ ШИФРІВ. ОСНОВНІ ВИМОГИ ЩОДО ПОБУДОВИ БСШ ...... 8 1.1 Основні вимоги щодо побудови БСШ .. 8 1.2 Класифікація атак на БСШ .... 9 1.3 Лінійний криптоаналіз ...11 1.4 Диференціальний криптоаналіз ....17 1.5 Методика оцінки БСШ ...21 РОЗДІЛ 2 ДОСЛІДЖЕННЯ ЕФЕКТИВНОСТІ АЛГОРИТМІВ БСШ НА ОСНОВІ МІНІ-ВЕРСІЙ .... 24 2.1 Аналіз можливості використання міні-версій алгоритмів БСШ ... 24 2.2. Аналіз побудови S-боксів для міні-версій БСШ ..27 РОЗДІЛ 3 ОЦІНКА АДЕКВАТНОСТІ ВИКОРИСТАННЯ МІНІ-ВЕРСІЙ БСШ НА ОСНОВІ ВИКОРИСТАННЯ ПОВНИХ ШИФРІВ .... 32 3.1 Розробка програмного пакету для проведення можливості використання міні-версій БСШ ... 32 3.2 Результати досліджень використання міні-версій для оцінки ефективності БСШ .... 35 3.3 Аналіз показників оцінки повних диференціалів ....41 3.4 Дослідження статистичних властивостей міні-версій на основі пакету NIST STS 822 ...46 РОЗДІЛ 4. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ ...49 4.1. Охорона праці ...49 4.2. Безпека в надзвичайних ситуаціях ....51 ВИСНОВКИ ...55 Список літератури ...56 Додатки .... 62
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Su, Dong-Po, and 蘇東波. "A Study on Symmetric Block Cipher Scheme with Preimplemented Substitution Boxes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/46193517794089583865.
Full textAbstract:
碩士國防大學
資訊管理學系
103
Information technology is rapidly developing nowadays; it is a trend for people to use more digitialized documentations in their life and jobs. Therefore, it becomes important that how to protect these digitialized documentations. Data encryption is a good solution to protect confidentiality of these digitialized documentations. However, there exists a process overhead for data encryption. This study proposes an encryption scheme with preimplemented substitution boxes / inverse substitution boxes to enhance data encryption performance. In this study, we use random numbers to generate a million of different substitution boxes / inverse substitution boxes and store them in files. The proposed encryption scheme will base on these preimplemented substitution boxes / inverse substitution boxes to perform a data encryption process. Moreover, for realizing encryption performance of the proposed encryption scheme, we execute a comparison of data encryption processes without preimplemented substitution boxes / inverse substitution boxes. This study implements the proposed encryption scheme with C. We base on several possible scenarios, different sizes of substitution boxes / inverse substitution boxes and different types of files, to perform many data encryption processes and collect the encryption / decryption performance data. Analyzing the collected encryption / decryption performance data, we found that the proposed encryption scheme can receive better performance with a large size (16 * 16) of substitution boxes / inverse substitution boxes.
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Jhou, Hsu-Tung, and 周旭東. "A study on pseudo random-based symmetric block cipher encryption scheme." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/30741494888101813673.
Full textAbstract:
碩士國防管理學院
國防資訊研究所
96
As information security becomes more important, many encryption mechanisms were proposed to assure confidentiality of documentations. Encryption mechanisms can be divided into two branches, symmetric encryption and asymmetric encryption. Block cipher is one of major symmetric encryption schemes, another scheme is stream cipher. So far, Advanced Encryption Standard (AES) is a famous block cipher; it is accepted as one of block cipher schemes which are more secure and more reliable. This study tries to base on AES to propose an AES-alike block cipher scheme with pseudo random number generator. In the proposed encryption scheme, 3 measures, byte substitution, block scramble, and add round keys with XOR, are adopted sequentially to perform encryption process. In the decryption process, the 3 measures will be performed in an inverse sequence to decrypt ciphertexts. Moreover, the 3 measures operations require their corresponding parameters, substitution box / inverse substitution box, shift settings, and round keys, to process encryption / decryption operations. These encryption / decryption parameters are generated with a LCG random number generator. For ensuring to generate the same random number serial in the encryption / decryption processes, users need input the same unit code, passphrase, and timestamp as the premaster secrets in the propose encryption / decryption scheme. With the same premaster secrets, the same random number serial can be generated by the LCG random number generator to have corresponding encryption / decryption parameters. With corresponding encryption / decryption parameters, the proposed encryption / decryption scheme can encryption / decryption process well and efficiently. In this study, a prototype program is implemented with C and C# to understand the feasibility of the proposed block cipher mechanism. With the execution results, it shows that the proposed block cipher scheme can perform encryption / decryption process very well.
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Deng, Ming-Yan, and 鄧名言. "A Study on Symmetric Encryption Scheme with Enhanced Pseudo Random Number and Streaming Cipher Skill." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/85725720948282412930.
Full textAbstract:
碩士國防大學管理學院
資訊管理學系
97
Symmetric encryption schemes can be divided into two branches; one is a block cipher scheme and the other is a streaming cipher scheme. It depends on data features to use a block cipher scheme or a streaming cipher scheme to encrypt data. Usually, for streaming data, a streaming cipher scheme is adopted to handle a data encryption process. Right now, many streaming applications emerge over the Internet; it shows that a streaming cipher scheme becomes more important. In this study, we propose a streaming cipher scheme with an enhanced LCG pseudo random number generator. General speaking, a good streaming cipher scheme depends on a robust pseudo random number generator (PRNG). The linear congruential generator (LCG) is a widely used pseudo random generator; it is simple and fast; however, it is easily to be attacked by opponents. Thus, an enhanced algorithm of LCG PRNG is proposed in this study to reduce crack probability of a LCG algorithm. With the proposed enhanced LCG PRNG, the cryptanalysis possibility of the proposed streaming cipher scheme can be reduced. In this study, a frequency test and a chi-square test are used to improve the proposed enhanced LCG PRNG. Moreover, this study also proposes several streaming cipher processes to strengthen data encryption complexity. Finally, a prototype of the proposed streaming encryption scheme is implemented with C and C#.
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Chen, Hsien Chou, and 陳憲洲. "A Study on Cipher Block Chaining Symmetric Block Encryption Scheme with Dynamic Pseudo Random Numbers." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/29758544020313816966.
Full textAbstract:
碩士國防大學管理學院
資訊管理學系
99
For military information staffs, the information security is an important issue needs to be understood very well in the R.O.C. military. There are many information security attacks from the P.R.O.C. cyber forces and their attack skills keep refining and changing. Although many information security defense mechanisms, such as: firewall, invasion protection system, and antivirus software, are adopted to assure the information security of the military. However, for the military, it is still possible that confidential information can be eavesdropped through networks or media storages. Therefore, it is an important issue for the military to protect confidentiality of classified information. The encryption scheme is one good solution for the military to achieve information confidentiality. This study proposes a CBC(cipher-block chaining)-based block symmetric encryption scheme. The proposed encryption scheme depends on an input password to support a dynamic combination of encryption/decryption function modules with LCG random number generator. With different password, a different combination of encryption/decryption function modules is adopted to encrypt/decrypt data. We implement the proposed encryption scheme with C and C#. For understanding the performance of the proposed encryption scheme, the several scenarios are executed and the encryption performance is compared to AES scheme. Keywords: CBC, Symmetric block encryption, Random number generator, Linear congruential generator