Full-Round Differential Attack on the Original Version of the Hash Function Proposed at PKC'98

Shin et al.[4] proposed a new hash function with 160-bit output length at PKC'98. Recently, at FSE 2002, Han et al.[5] cryptanalyzed the hash function proposed at PKC'98 and suggested a method finding a collision pair with probability 2-30, supposing that boolean functions satisfy the SAC(Strict Avalanche Criterion). This paper improves their attack and shows that we can find a collision pair from the original version of the hash function with probability 2-37.13 through the improved method. Furthermore we point out a weakness of the function comes from shift values dependent on message.