Basic cryptanalysis methods on block ciphers

Çelik, Dilek
Differential cryptanalysis and linear cryptanalysis are the first significant methods used to attack on block ciphers. These concepts compose the keystones for most of the attacks in recent years. Also, while designing a cipher, these attacks should be taken into consideration and the cipher should be created as secure against them. Although di fferential cryptanalysis and linear cryptanalysis are still important, they started to be ine cient due to the improvements in the technology. So, these attacks are extended. For instance, higher order diff erential cryptanalysis, truncated di fferential cryptanalysis, generalized linear cryptanalysis, partitioning linear cryptanalysis, linear cryptanalysis using multiple linear approximations are introduced as the extended versions of these attacks. There exists significant applications of these extended attacks. Algebraic attack is a method of cryptanalysis that consists of obtaining a representation of the cipher as a system of equations and then, solving this system. Up to today, just a few attacks that are practically possible to mount are presented. However, due to the fact that algebraic cryptanalysis requires only a handful of known plaintexts to perform, it is a promising and significant attack. This thesis is a survey covering all the methods of attacks described above. Illustrations and summaries of some important papers including these cryptanalysis techniques are given.


On statistical analysis of synchronous stream ciphers
Sönmez Turan, Meltem; Doğanaksoy, Ali; Department of Cryptography (2008)
Synchronous stream ciphers constitute an important class of symmetric ciphers. After the call of the eSTREAM project in 2004, 34 stream ciphers with different design approaches were proposed. In this thesis, we aim to provide a general framework to analyze stream ciphers statistically. Firstly, we consider stream ciphers as pseudo random number generators and study the quality of their output. We propose three randomness tests based on one dimensional random walks. Moreover, we theoretically and experimenta...
Combined attacks on block ciphers
Öztop, Neşe; Doğanaksoy, Ali; Department of Cryptography (2009)
Cryptanalytic methods are very important tools in terms of evaluating the security of block ciphers in a more accurate and reliable way. Differential and linear attacks have been the most effective cryptanalysis methods since the early 1990s. However, as the technology developed and more secure ciphers are designed, these fundamental methods started to be not so efficient. In order to analyze the ciphers, new methods should be introduced. One approach is inventing new techniques that are different from the ...
Impossible differential cryptanalysis of reduced round HIGHT
Tezcan, Cihangir; Doğanaksoy, Ali; Department of Cryptography (2009)
Design and analysis of lightweight block ciphers have become more popular due to the fact that the future use of block ciphers in ubiquitous devices is generally assumed to be extensive. In this respect, several lightweight block ciphers are designed, of which HIGHT is proposed by Hong et al. at CHES 2006 as a constrained hardware oriented block cipher. HIGHT is shown to be highly convenient for extremely constrained devices such as RFID tags and sensor networks and it became a standard encryption algorithm...
Improved improbable differential attacks on ISO standard CLEFIA: Expansion technique revisited
Tezcan, Cihangir (2016-02-01)
Improbable differential cryptanalysis is a recent attack technique that generalizes impossible differential cryptanalysis for block ciphers. In this paper, we give the most effective attacks known to date on the CLEFIA cipher using improbable differential cryptanalysis. Moreover, we provide a general data complexity calculation that can guide the cryptanalyst to choose the optimal improbable differential. On a related account, we consider the probability calculations used for improbable differential cryptan...
Some generalized multipartite access structures
Kaşkaloğlu, Kerem; Özbudak, Ferruh; Department of Cryptography (2010)
In this work, we study some generalized multipartite access structures and linear secret sharing schemes for their realizations. Given a multipartite set of participants with m compartments (or levels) and m conditions to be satisfied by an authorized set, we firstly examine the intermediary access structures arousing from the natural case concerning that any c out of m of these conditions suffice, instead of requiring anyone or all of the m conditions simultaneously, yielding to generalizations for both th...
Citation Formats
D. Çelik, “Basic cryptanalysis methods on block ciphers,” M.S. - Master of Science, Middle East Technical University, 2010.