International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 17 June 2015

Bingke Ma, Bao Li, Rongl
ePrint Report ePrint Report
In this paper, we present improved preimage attacks on the reduced-round \\texttt{GOST} hash function family, which serves as the new Russian hash standard, with the aid of techniques such as the rebound attack, the Meet-in-the-Middle preimage attack and the multicollisions. Firstly, the preimage attack on 5-round \\texttt{GOST-256} is proposed which is the first preimage attack for \\texttt{GOST-256} at the hash function level. Then we extend the (previous) attacks on 5-round \\texttt{GOST-256} and 6-round \\texttt{GOST-512} to 6.5 and 7.5 rounds respectively by exploiting the involution property of the \\texttt{GOST} transposition operation.

Secondly, inspired by the preimage attack on \\texttt{GOST-256}, we also study the impacts of four representative truncation patterns on the resistance of the Meet-in-the-Middle preimage attack against \\texttt{AES}-like compression functions, and propose two stronger truncation patterns which make it more difficult to launch this type of attack. Based on our investigations, we are able to slightly improve the previous pseudo preimage attacks on reduced-round \\texttt{Gr{\\o}stl-256}.

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