Impossible Differential Attacks on 13-Round CLEFIA-128

CLEFIA, a new 128-bit block cipher proposed by Sony Corporation, is increasingly attracting cryptanalysts’ attention. In this paper, we present two new impossible differential attacks on 13 rounds of CLEFIA-128. The proposed attacks utilize a variety of previously known techniques, in particular the hash table technique and redundancy in the key schedule of this block cipher. The first attack does not consider the whitening layers of CLEFIA, requires 2^109.5 chosen plaintexts, and has a running time equivalent to about 2^112.9 encryptions. The second attack preserves the whitening layers, requires 2^117.8 chosen plaintexts, and has a total time complexity equivalent to about 2^121.2 encryptions.