Hash functions are taking important roles in cryptography and have been used in many applications, e.g., digital signatures, authentications and message integrity. Since the break of MD5 and SHA-1, cryptographers have been searching for secure and efficient hash functions. Developed from GOST, GOST R is the hash function standard of Russia. Similar as the structure of whirlpool, it also uses an AES-like block cipher in its compression function. Rebound attack is a freedom degrees utilized technique which can be applied to find collisions in both permutation based and block cipher based hash constructions.