A New Herding Attack on Hash Functions with Strengthening Merkle-Damagard (MD) Construction
对强化MD结构杂凑函数的一个新的“牧群”攻击

This paper constructs a “diamond structure” multicollision with 2k initial values and variant lengths, which is used to propose a new chosen target forced prefix preimage attack (herding attack) on hash functions with Strengthening Merkle-Damagard (SMD) construction to find a preimage with 2k+3 blocks. Since the number of the chaining values available in herding attack is increased, the computational complexity of herding attack is reduced to O(2n-k/3+2n/2+k+2) from O(2n-2(k+1)+2n/2+k+5/2) for k≥n/4-1.05.