New impossible differential attacks on Camellia

Abstract

Camellia is one of the most worldwide used block ciphers, which has been selected as a standard by ISO/IEC. In this paper, we propose several new 7-round impossible differentials of Camellia with 2 FL/FL -1 layers, which turn out to be the first 7-round impossible differentials with 2 FL/FL -1 layers. Combined with some basic techniques including the early abort approach and the key schedule consideration, we achieve the impossible differential attacks on 11-round Camellia-128, 11-round Camellia-192, 12-round Camellia-192, and 14-round Camellia-256, and the time complexity are 2 123.8, 2 121.7, 2 171.4 and 2 238.3 respectively. As far as we know, these are the best results against the reduced-round variants of Camellia. Especially, we give the first attack on 11-round Camellia-128 reduced version with FL/FL -1 layers. © 2012 Springer-Verlag.