Preimage Attack on Hash Function RIPEMD

摘要

RIPEMD is a cryptographic hash function devised in the framework of the RIPE project (RACE Integrity Primitives Evaluation, 1988-1992). It consists of two parallel lines, and each line is identical to MD4 except for some internal constants. It has been broken by the collision attack, but no preimage attack was given. In this paper, we give a preimage attack on the compression function of the 26-step reduced RIPEMD with complexity 2~(110) compression function computations, and we extend the attack on the compression function to an attack on the 26-step reduced RIPEMD with complexity 2~(115.2) instead of 2~(128). Then we extend the attack on 26 steps to the attack on 29 steps with the same complexity. Moreover, we can reduce the complexity of the preimage attack on the full RIPEMD without the padding rule by 1 bit compared with the brute-force attack.