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Hybrid key-combiner for network traffic
Mogrovics, Alexander ; Dzurenda, Petr (referee) ; Ricci, Sara (advisor)
Klasická kryptografie se opírá převážně o celočíselnou faktorizaci (IF), která využívá RSA, a problém diskrétního logaritmu (DLP), na jehož principu funguje protokol Diffie- Hellman. Bezpečnost těchto problémů je ohrožena nástupem kvantových počítačů. Například Shorrův algoritmus je schopen řešit IF i DLP v polynomiálním čase. Cílem této práce je prostudovat schémata, která patří do klasické kryptografie a postkvantové kryptografie, aby bylo možné implementovat navrhovaný hybridní slučovač klíčů. Tento slučovač klíčů využívá klíče ze schémat QKD, Kyber a ECDH a interně používá SHA-3 a HMAC.
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Algebraic-differential analysis of Keccak
Seidlová, Monika ; Göloglu, Faruk (advisor) ; Hojsík, Michal (referee)
In this thesis, we analyze the cryptographic sponge function family Keccak - the winner of the SHA-3 Cryptographic Hash Standard competition. Firstly, we explore how higher order differentials can be used to forge a tag in a parallelizable MAC function. We introduce new terms and theory studying what affine spaces remain affine after one round of Keccak's underlying permutation Keccak-f. This allows us to improve the forgery. Secondly, collisions in Keccak could be generated from pairs of values, that follow particular differential trails in Keccak-f. We tested finding pairs for a given differential trail in reduced-round Keccak-f using algebraic techniques with the mathematics software SAGE. We found a pair in a 4-round trail in Keccak-f[50] in under 5 minutes and a 3-round trail in Keccak-f[100] in 80 seconds on a regular PC. Powered by TCPDF (www.tcpdf.org)
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Testování náhodnosti a použití statistických testů v kryptografii
Nižnanský, Petr ; Růžička, Pavel (advisor) ; Holub, Štěpán (referee)
Pseudorandom generators belong to the primary focus of cryptology. The key to every cipher has to be generated at random, otherwise the security of the whole cipher is threatened. Another point of importance is the pseudorandom generators' close relationship to the stream ciphers. In this work, we first introduce statistical theory related to randomness testing. Then, we describe 8 classical statistical tests. We introduce a concept of next bit testing and derive variants of previous tests. Moreover, with this new battery of tests we examine the randomness of SHA-3 second round candidates and present the results. Also a sensitivity of tests is investigated and several useful transformations are shown. Powered by TCPDF (www.tcpdf.org)
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Analýza návrhu nových hašovacích funkcí pro soutěž SHA-3
Marková, Lucie ; Tůma, Jiří (advisor) ; Hojsík, Michal (referee)
In the present work we study a linearization framework for assessing the security of hash functions and analyze the proposal of hash function BLAKE. The thesis demonstrates a limitation of a method presented in the linearization framework for which the method could not be applied to the full extent. Further in the thesis, it is explained how to find a message difference for second preimage attack with the help of linear codes. To that end, a matrix representing the linearized compression function of BLAKE is constructed. My thesis as a PDF file and source codes of computations that I created in Mathematica software are on an enclosed CD.
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