CUBE testers on hash functions

Abstract

Hashing Algorithms are of prime importance these days due to their implementation in applications requiring data authentication and data forgery detection and prevention. Without safeguards such as those offered by hash functions, data would be extremely vulnerable to attacks which can alter or make changes in it. ‘Cube Testers’ Attack is a latest technique which is being utilized to test different cryptosystems, both ciphers and hashes for non-randomness behavior. The attack distinguishes a family of functions from random functions using some testable properties like Balanced-ness, Constant-ness, presence of Low Degree, Linear Variables and presence of Neutral Variables. As pseudorandom object has low correlation with a structured object so it gives distinguishers that help finding nonrandomness in the hashes. Implementation of Cube testers is possible with black box access that is it can be independent of internal structure. SHA-256 is the standard hash function recommended by NIST in 2002. It has been tested against different cryptanalytic techniques including collision, pseudo collision, preimage and second preimage attacks. It has been tested against Cube Testers for the first time. SHA-256 is tested against three properties using Cube Testers, Balance-ness, Impedance and Off By One. Reduced version of SHA-256 with 25 steps out of 64 steps has shown non-random behavior against Balance Test. Complete 64 step SHA-256 is found vulnerable against Impedance Test. Off By One test could not find any weakness against SHA-256.