Attacks on a double length blockcipher-based hash proposal

摘要

In this paper we attack a 2n-bit double length hash function proposed by Lee et al. This proposal is a blockcipher-based hash function with hash rate 2/3. The designers claimed that it could achieve ideal collision resistance and gave a security proof. However, we find a collision attack with complexity of O(23n/4) and a preimage attack with complexity of O(2 n ). Our result shows this construction is much worse than an ideal 2n-bit hash function.