Paper 2015/959 Original: eprint.iacr.org/2015/959 ↗

Cryptanalysis of the Round-Reduced Kupyna Hash Function

Abstract

The Kupyna hash function was selected as the new Ukrainian standard DSTU 7564:2014 in 2015. It is designed to replace the old Independent States (CIS) standard GOST 34.311-95. The Kupyna hash function is an AES-based primitive, which uses Merkle-Damgård compression function based on Even-Mansour design. In this paper, we show the first cryptanalytic attacks on the round-reduced Kupyna hash function. Using the rebound attack, we present a collision attack on 5-round of the Kupyna-256 hash function. The complexity of this collision attack is ($2^{120},2^{64}$) (in time and memory). Furthermore, we use guess-and-determine MitM attack to construct pseudo-preimage attacks on 6-round Kupyna-256 and Kupyna-512 hash function, respectively. The complexity of these preimage attacks are ($2^{250.33},2^{250.33}$) and ($2^{498.33},2^{498.33}$) (in time and memory), respectively.