Cryptanalysis of the HaF family of hash functions

Abstract

HaF is a family of hash functions developed by prof. Stokłosa and his team from Institute of Control and Information Engineering of Poznań University of Technology. HaF is classical Merkle-Damgård construction with output sizes of 256, 512 or 1024 bits. In this paper we will present an attack on all the members of HaF family with negligible complexity (collision for all the members can be found without using a computer). We will also show that the improved function (without the critical transformation) is still insecure. It is possible to find a preimage for short messages. We can also create some fixed points, with a complexity of single compression function call.