GOST (hash function)

The GOST hash function is a 256-bit cryptographic hash function defined in the Russian national standard GOST R 34.11-94, Information Technology, Cryptographic Information Security, Hash Function. The equivalent standard used by other member states of the Commonwealth of Independent States is GOST 34.311-95. It is built on the GOST block cipher and must not be confused with the later Streebog hash function of the revised standard GOST R 34.11-2012. A message of any length is split into 256-bit blocks, the last block padded with zeros, and each block is run through a step hash function that generates four keys, enciphers the running hash value with them and then shuffles the result. Along the way the algorithm keeps a running 256-bit sum of all blocks and the message length in bits, and at the end it hashes the length and then the sum to produce the final digest. A 2008 cryptanalysis paper reported a collision attack and preimage attacks against the full-round function.