Impossible Differential Attack on Reduced Round SPARX-64/128

SPARX-64/128 is an ARX-based block cipher with 64-bit block size and 128-bit key. It was published in Asiacrypt 2016 as one of the instantiations of a family of ARX-based block ciphers with provable security against single-characteristic differential and linear cryptanalysis. In this work, we present 12 and 13-round impossible distinguishers on SPARX-64/128 that can be used to attack 15 and 16-round SPARX64/128 with post-whitening keys, respectively. While the 15-round attack starts from round 0, the 16-round one, exploiting the key schedule, has to start from round 2.