Improved results on impossible differential cryptanalysis of reduced-round Camellia-192/256
As an international standard adopted by ISO/IEC, the block cipher Camellia has been used in various cryptographic applications. In this paper, we reevaluate the security of Camellia against impossible differential cryptanalysis. Specifically, we propose several 7-round impossible differentials with the FL/FL?1 layer. Based on one of them, we mount impossible differential attacks on 11-round Camellia-192 and 12-round Camellia-256. The data complexities of our attacks on 11-round Camellia-192 and 12-round Camellia-256 are about 2120 chosen plaintexts and 2119.8 chosen plaintexts, respectively. The corresponding time complexities are approximately 2167.1 11-round encryptions and 2220.87 12-round encryptions. As far as we know, our attacks are 216.9 times and 219.13 times faster than the previously best known ones but have slightly more data.
impossible differential cryptanalysis camellia block cipher