Paper 2015/896 Original: eprint.iacr.org/2015/896 ↗

Improved Attacks on Reduced-Round Camellia-128/192/256

Abstract

Camellia is a widely used block cipher, which has been selected as an international standard by ISO/IEC. In this paper, we consider a new family of dierentials of round-reduced Camellia-128 depending on dierent key subsets. There are totally 224 key subsets corresponding to 224 types of 8-round dierentials, which cover a fraction of 1- 1=2^{15} of the keyspace. And each type of 8-round dierential consists of 2^{43} dierentials. Combining with the multiple dierential attack techniques, we give the key-dependent multiple dierential attack on 10-round Camellia-128 with data complexity 2^{91} and time complexity 2^{113}. Furthermore, we propose a 7-round property for Camellia-192 and an 8-round property for Camellia-256, and then mount the meet-in-the-middle attacks on 12-round Camellia-192 and 13-round Camellia-256, with complexity of 2^{180} encryptions and 2^{232.7} encryptions, respectively. All these attacks start from the rst round in a single keysetting.