Practical Pseudo-collisions for Hash Functions ARIRANG-224/384

In this paper we analyse the security of the SHA-3 candidate ARIRANG. We show that bitwise complementation of whole registers turns out to be very useful for constructing high-probability differential characteristics in the function. We use this approach to find nearcollisions with Hamming weight 32 for the full compression function as well as collisions for the compression function of ARIRANG reduced to 26 rounds, both with complexity close to 2 and memory requirements of only a few words. We use near collisions for the compression function to construct pseudo-collisions for the complete hash functions ARIRANG224 and ARIRANG-384 with complexity 2 and close to 2, respectively. We implemented the attacks and provide examples of appropriate pairs of H,M values. We also provide possible configurations which may give collisions for step-reduced and full ARIRANG.