Multicollision Attack on a recently proposed hash function vMDC-2

Abstract

In this paper, we describe an attack on a new double block length hash function which was proposed as a variant of MDC-2 and MDC-4. The vMDC-2 compression function is based on two calls to a block cipher that compresses a 3n-bit string to a 2n-bit one. This attack is based on the Joux's multicollision attack, where we show that an adversary wins finding collision game by requesting $2^{70}$ queries for $ n=128$-bit block cipher that is much less than the complexity of birthday attack.