Cryptanalysis of ESSENCE

ESSENCE is a hash function submitted to the NIST Hash Competition that stands out as a hardware-friendly and highly parallelizable design. Previous analysis showed some non-randomness in the compression function which could not be extended to an attack on the hash function and ESSENCE remained unbroken. Preliminary analysis in its documentation argues that it resists standard differential cryptanalysis. This paper disproves this claim, showing that advanced techniques can be used to significantly reduce the cost of such attacks: using a manually found differential characteristic and an advanced search algorithm, we obtain collision attacks on the full ESSENCE-256 and ESSENCE512, with respective complexities 2 and 2. In addition, we show how to use these attacks to forge valid (message, MAC) pairs for HMACESSENCE-256 and HMAC-ESSENCE-512, essentially at the same cost as a collision.