Attacks on StreamHash 2

StreamHash 2 is a hash function proposed by Michał Trojnara at the Cryptography and Security Systems in 2011 Conference. This algorithm is a member of StreamHash family which was first introduced in 2008 during the SHA-3 Competition. In this paper we will show collision attacks on the internal state of the StreamHash 2 hash function with complexity about 2 for the 32n-bit version of the algorithm and its reduced version with complexity 2. We will also show its application to attacking the full StreamHash 2 function (finding a collision on all output bits) with complexity about 2 . We will try to show that any changes made to the construction (for instance the ones proposed for StreamHash 3) will have no effect on the security of the family due to critical fault build into the compression function. 1 StreamHash and the SHA-3 Competition On November 2nd, 2007 the National Institute of Standards and Technology (NIST) announced a hash function competition for a new SHA-3 (Secure Hash Algorithm). The goal of the competition was to replace the older constructions such as SHA-1 and SHA-2 in all their variants with a new, more secure and faster algorithm. Another goal of the competition was to improve knowledge in the field of hash functions and find new attacks and new constructions for hash functions. There were over 50 proposed algorithms and 51 of them were selected for the first round. One of those 51 candidates was StreamHash (now, due to the family development, called StreamHash 1) proposed by Michał Trojnara from Warsaw University of Technology. ∗[email protected] Pobrane z czasopisma Annales AIInformatica http://ai.annales.umcs.pl Data: 29/12/2017 00:03:25