Multicollision Attacks on Generalized Hash Functions

In a recent paper in crypto-04, A. Joux [6] showed a multicollision attacks on the classical iterated hash function. He also showed how the multicollision attack can be used to get a collision attack on the concatenated hash function. In this paper we have shown that the multicollision attacks exist in a general class of sequential or tree based hash functions even if message blocks are used twice unlike the classical hash function.