In this paper, we propose a systematic search method for finding the impossible differential characteristic for block cipher structures, better than the U-method introduced by Kim et al [6]. This method is referred as unified impossible differential (UID) cryptanalysis. We give practical UID

. Then we discuss that this change in the impossible differential cryptanalysis is commodious and rational when the data complexity is low and time complexity is marginal. 1

Abstract. Several recently proposed ciphers, for example Rijndael and Serpent, are built with layers of small S-boxes interconnected by linear key-dependent layers. Their security relies on the fact, that the classical methods of cryptanalysis (e.g. linear or differential attacks) are based

Block ciphers are the very foundation of computer and information security. FOX, also known as IDEA NXT, is a family of block ciphers published in 2004 and is famous for its provable security to cryptanalysis. In this paper, we apply impossible differential cryptanalysis on FOX cipher. We find a 4

Abstract. This paper reports impossible differential cryptanalysis on the 128-bit block cipher CLEFIA that was proposed in 2007, including new 9-round impossible differentials for CLEFIA, and the result of an impossible differential attack using them. For the case of a 128-bit key, it is possible

Abstract. Impossible differential cryptanalysis is a very popular tool for analyzing the security of modern block ciphers and the core of such attack is based on the existence of impossible differentials. Currently, most methods for finding impossible differentials are based on the miss

This report gives a basic introduction to block cipher design and analysis. The concepts and design principles of block ciphers are explained, particularly the class of block ciphers known as Feistel ciphers. Some modern block cipher cryptanalysis methods are demonstrated by applying them

Abstract. TEA, XTEA and HIGHT are lightweight block ciphers with 64-bit block sizes and 128-bit keys. The round functions of the three ciphers are based on the simple operations XOR, modular addition and shift/rotation. TEA and XTEA are Feistel ciphers with 64 rounds designed by Needham and Wheeler

These doctoral studies were conducted under the supervision of Prof. Chris Mitchell. The work presented in this thesis is the result of original research carried out by myself, in collaboration with others, whilst enrolled in the Information Security Group of Royal Holloway, University of London as a candidate for the degree of Doctor of Philosophy. This work has not been submitted for any other degree or

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