New Impossible Differential Attacks of Reduced-Round Camellia-192 and Camellia-256

Camellia is a block cipher selected as a standard by ISO/IEC, which has been analyzed by a number of cryptanalysts. In this paper, we propose several 6-round impossible differential paths of Camellia with the FL/FL−1 layer in the middle of them. With the impossible differential and a well-organized precomputational table, impossible differential attacks on 10-round Camellia-192 and 11-round Camellia-256 are given, and the time complexity are 2 and 2 respectively. An impossible differential attack on 15-round Camellia-256 without FL/FL−1 layers and whitening is also be given, which needs about 2 encryptions. To the best of our knowledge, these are the best cryptanalytic results of Camellia-192/-256 with FL/FL−1 layers and Camellia-256 without FL/FL−1 layers to date.