Impossible differential attack is one of powerful methods for analyzing block ciphers. When designing block ciphers, it must be safe for impossible differential attacks. In case of impossible differential attack, the attack starts from finding the impossible differential characteristic. However, in the case of the ARX-based block cipher, these analyzes were difficult due to the addition of modu...

MISTY1 is a Feistel block cipher that received a great deal of cryptographic attention. Its recursive structure, as well as the added FL layers, have been successful in thwarting various cryptanalytic techniques. The best known attacks on reduced variants of the cipher are on either a 4-round variant with the FL functions, or a 6-round variant without the FL functions (out of the 8 rounds of th...

In this paper, we present several new related-key impossible differential attacks on 7and 8-round AES-192, following the work of Eli Biham and Orr Dunkelman et al. [1]. We choose another relation of the two related keys, start attacks from the very beginning(instead of the third round in [1]) so as to improve the data and time complexities of their attacks. Furthermore, we point out and correct...

In this paper we examine the strength of AES-256 against the related-key impossible differential attack, following the work in [1] and [2]. Firstly, we present a carefully chosen relation between the related keys, which can be extended to 8-round(even more rounds) subkey differences. Then, we construct a 5.5-round related-key impossible differential. Using the differential, we present an attack...

In this paper we examine the strength of AES against the related-key impossible differential attack, following the work of Jakimoski and Desmedt [12]. We use several additional observations to substantially improve the data and time complexities of their attacks. Amongst our results, we present a related-key attack on 7-round AES-192 with data complexity of 2 chosen plaintexts (instead of 2). O...

In this paper, we improve the impossible differential attack on 20-round LBlock given in the design paper of the LBlock cipher. Using relations between the round keys we attack on 21-round and 22-round LBlock with a complexity of 2 and 2 encryptions respectively. We use the same 14-round impossible differential characteristic observed by the designers to attack on 21 rounds and another 14-round...

Impossible differential attack is a well-known mean to examine robustness of block ciphers. Using impossible differ- ential cryptanalysis, we analyze security of a family of lightweight block ciphers, named Midori, that are designed considering low energy consumption. Midori state size can be either 64 bits for Midori64 or 128 bits for Midori128; however, both vers...

Impossible differential attacks against Rijndael and Crypton have been proposed up to 5-round. In this paper we expand the impossible differential attacks to 6-round. Although we use the same 4-round impossible differential as in five round attacks, we put this impossible differential in the middle of 6-round. That is, we will consider one round before the impossible differential and one more r...