An improved impossible differential cryptanalysis of Zodiac

Abstract

In this paper, we introduce a new impossible differential cryptanalysis of Zodiac that is considerably more effective than the one in the previous work ( Hong et al., 2002). Using two new 13-round impossible differential characteristics and the early abort technique, this 3R-Attack breaks 128-bit key full-round Zodiac with complexity less than 2 71.3 encryptions, which is practical. This result is approximately 2 48 times better than what mentioned in the earlier work. Our result reveals depth of Zodiac’s weakness against impossible differential cryptanalysis due to its poor diffusion layer. We also obtain a tighter upper bound for time complexity.