Paper 2006/413

Preimage Attack on Parallel FFT-Hashing

Donghoon Chang

Abstract

Parallel FFT-Hashing was designed by C. P. Schnorr and S. Vaudenay in 1993. The function is a simple and light weight hash algorithm with 128-bit digest. Its basic component is a multi-permutation which helps in proving its resistance to collision attacks. % In this work we show a preimage attack on Parallel FFT-Hashing with complexity $2^{t+64}+2^{128-t}$ and memory $2^{t}$ which is less than the generic complexity $2^{128}$. When $t=32$, we can find a preimage with complexity $2^{97}$ and memory $2^{32}$. Our method can be described as ``disseminative-meet-in-the-middle-attack'' we actually use the properties of multi-permutation (helpful against collision attack) to our advantage in the attack. Overall, this type of attack (beating the generic one) demonstrates that the structure of Parallel FFT-Hashing has some weaknesses when preimage attack is considered. To the best of our knowledge, this is the first attack on Parallel FFT-Hashing.