Preimage Attacks against PKC98-Hash and HAS-V

摘要

We propose preimage attacks against PKC98-Hash and HAS-V. PKC98-Hash is a 160-bit hash function proposed at PKC 1998, and HAS-V, a hash function proposed at SAC 2000, can produce hash values of 128 + 32fc (k = 0,1,..., 6) bits. These hash functions adopt the Merkle-Damgard and Davies-Meyer constructions. One unique characteristic of these hash functions is that their step functions are not injec-tive with a fixed message. We utilize this property to mount preimage attacks against these hash functions. Note that these attacks can work for an arbitrary number of steps. The best proposed attacks generate preimages of PKC98-Hash and HAS-V-320 in 296 and 2256 compression function computations with negligible memory, respectively. This is the first preimage attack against the full PKC98-Hash function.