Meet-in-the-Middle Technique for Truncated Differential and Its Applications to CLEFIA and Camellia

摘要

As one of the generalizations of differential cryptanalysis, the truncated differential cryptanalysis has become a powerful toolkit to evaluate the security of block ciphers. In this article, taking advantage of the meet-in-the-middle like technique, we introduce a new method to construct truncated differential characteristics of block ciphers. Based on the method, we propose 10-round and 8-round truncated differential characteristics for CLEFIA and Camellia, respectively, which are ISO standard block ciphers. Applying the 10-round truncated differential characteristic for CLEFIA, we launch attacks on 14/14/15-round CLEFIA-128/192/256 with 2~(108), 2~(135) and 2~(203) encryptions, respectively. For Camellia, we utilize the 8-round truncated differential to attack 11/12-round Camellia-128/192 including the FL/FL~(-1) and whiten layers with 2~(121.3) and 2~(185.3) encryptions. As far as we know, most of the cases are the best results of these attacks on both ciphers.