Single Block Attacks and Statistical Tests on CubeHash

This paper describes a second preimage attack on the CubeHash cryptographic one-way hash function. The attack finds a second preimage in less time than brute force search for these CubeHash variants: CubeHash r/b-224 for b > 100; CubeHashr/b-256 for b > 96; CubeHashr/b-384 for b > 80; and CubeHashr/b-512 for b > 64. However, the attack does not break the CubeHash variants recommended for SHA-3. The attack requires minimal memory and can be performed in a massively parallel fashion. This paper also describes several statistical randomness tests on CubeHash. The tests were unable to disprove the hypothesis that CubeHash behaves as a random mapping. These results support CubeHash’s viability as a secure cryptographic hash function.