对强化MD结构杂凑函数的一个新的“牧群”攻击

该文构造了具有2k个起始点的变长"钻石树"结构的多碰撞,并据此提出了对强化MD结构杂凑函数的一个新的选择目标强制前缀且原像长度为2k+3块的原像攻击(即"牧群"攻击).由于增大了攻击过程中可利用的中间链接值的数量,故当k≤n/4-1.05时,新的牧群攻击可将该攻击的计算复杂性由现有结果O(2n-2(k+1)+2n/2+k+5+2)降至O(2n-k/3+2n/2+k+2).

A New Herding Attack on Hash Functions with Strengthening Merkle-Damagard (MD) Construction

This paper constructs a “diamond structure” multicollision with 2^k 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(2^n-k/3+2^n/2+k+2) from  O(2^n-2(k+1)+2^n/2+k+5/2) for k≥n/4-1.05.