Cryptanalysis of CLEFIA using multiple impossible differentials

This paper reports impossible differential cryptanalysis on the 128-bit block cipher CLEFIA that was proposed in 2007. It is known that there are the 9-round impossible differentials in CLEFIA. This paper presents the several results of impossible differential attacks using multiple impossible differentials. For key lengths of 128, 192 and 256 bits, it is possible to apply impossible differential attacks to 12-round, 13-round and 14-round CLEFIA. For the case of a 128-bit key, this attack is the most efficient compared with previous results. For key lengths of 192 and 256 bits, the numbers of chosen plaintexts are the least.