Security of E2 against truncated differential cryptanalysis
This paper evaluates the security of the block cipher E2 against truncated differential cryptanalysis. We show an algorithm to search for effective truncated differentials. The result of the search confirmed that there exist no truncated differentials that lead to possible attacks for E2 with more than 8 rounds. The best attack breaks an 8-round variant of E2 with either IT-Function (the initial transformation) or FT-Function (the final transformation) using 2(94) chosen plaintexts. We also found the attack which distinguishes a 7-round variant of E2 with IT- and FT-Functions from a random permutation using 2(91) chosen plaintexts.
e2 truncated differential cryptanalysis search algorithm