Practical Collisions for SHAMATA-256
In this paper, we present a collision attack on the SHA-3 submission SHAMATA. SHAMATA is a stream cipher-like hash function design with components of the AES, and it is one of the fastest submitted hash functions. In our attack, we show weaknesses in the message injection and state update of SHAMATA. It is possible to find certain message differences that do not get changed by the message expansion and non-linear part of the state update function. This allows us to find a differential path with a complexity of about 296 for SHAMATA-256 and about 2110 for SHAMATA-512, using a linear low-weight codeword search. Using an efficient guess-and-determine technique we can significantly improve the complexity of this differential path for SHAMATA-256. With a complexity of about 240 we are even able to construct practical collisions for the full hash function SHAMATA-256.
KeywordsSHAMATA SHA-3 candidate hash function collision attack
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