Browsing by Subject "Block ciphers"
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Item Open Access Differential entropy analysis of the IDEA block cipher(Elsevier, 2014) Biryukov, A.; Nakahara, Jr. J.; Yıldırım H. M.This paper describes a new cryptanalytic technique that combines differential cryptanalysis with Shannon entropy. We call it differential entropy (DE). The objective is to exploit the non-uniform distribution of output differences from a given mapping as a distinguishing tool in cryptanalysis. Our preferred target is the IDEA block cipher, since we detected significantly low entropy at the output of its multiplication operation. We looked to further extend this entropy analysis to larger components and for a number of rounds. We present key-recovery attacks on up to 2.5-round IDEA in the single-key model and without weak-key assumptions. © 2013 Elsevier B.V. All rights reserved.Item Open Access On probability of success in linear and differential cryptanalysis(Springer New York LLC, 2008-01) Selçuk, A. A.Despite their widespread usage in block cipher security, linear and differential cryptanalysis still lack a robust treatment of their success probability, and the success chances of these attacks have commonly been estimated in a rather ad hoc fashion. In this paper, we present an analytical calculation of the success probability of linear and differential cryptanalytic attacks. The results apply to an extended sense of the term "success" where the correct key is found not necessarily as the highest-ranking candidate but within a set of high-ranking candidates. Experimental results show that the analysis provides accurate results in most cases, especially in linear cryptanalysis. In cases where the results are less accurate, as in certain cases of differential cryptanalysis, the results are useful to provide approximate estimates of the success probability and the necessary plaintext requirement. The analysis also reveals that the attacked key length in differential cryptanalysis is one of the factors that affect the success probability directly besides the signal-to-noise ratio and the available plaintext amount. © 2007 International Association for Cryptologic Research.