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 cryptanalysis on some popular block ciphers and give the detailed impossible differential characteristic...

We study applications of BV algorithm and present quantum versions of impossible differential cryptanalysis and truncated differential cryptanalysis based on it. Afterwards, we analyze their efficiencies and success probabilities rigorously. In traditional impossible differential attack or truncated differential attack, it is difficult to extend the differential path, which usually limits the n...

In this document we present a new way to bound the probability of occurrence of an n-round differential in the context of differential cryptanalysis. Hence this new model allows us to claim proof of resistance against impossible differential cryptanalysis, as defined by Biham and al. in 1999. This work will be described through the example of CS-Cipher, to which, assuming some non-trivial hypot...

We discuss the impossible differential cryptanalysis of the block cipher Zodiac [7]. The main design principles of Zodiac are simplicity and efficiency. However the diffusion layer in its round function is too simple to offer enough security. An impossible differential cryptanalysis is a proper method to attack the weakness of Zodiac. Our attack using two 14-round impossible characteristics der...

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-round impossible difference, by using which adversaries can attack 5, 6 and 7-round FOX64 with 2, ...

SKINNY is a new lightweight tweakable block cipher family proposed by Beierle et al. at CRYPTO 2016. SKINNY has 6 main variants where SKINNY-n-t is a block cipher that operates on n-bit blocks using t-bit tweakey (key and tweak) where n = 64 or 128 and t = n, 2n, or 3n. In this paper, we present impossible differential attacks against reduced-round versions of all the 6 members of the SKINNY fa...

Midori is a light weight block cipher recently presented by Banik et al in ASIACRYPT 2015. There are two versions of Midori with state sizes of 64-bit and 128-bit respectively. The round function is based on Substitution-Permutation Network(SPN). In this paper, we give impossible differential cryptanalysis of Midori64. We studied the non-linear layer of the cipher and give two useful properties...

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 to apply the impossible differential attack to CLEFIA reduced to 12 rounds. The number of chosen plaintexts r...

Standard differential cryptanalysis uses statistical dependencies between the difference of two plaintexts and the difference of the respective two ciphertexts to attack a cipher. Here we introduce polytopic cryptanalysis which considers interdependencies between larger sets of texts as they traverse through the cipher. We prove that the methodology of standard differential cryptanalysis can un...