Rebound Attacks on $$\textsf{SKINNY}$$ Hashing with Automatic Tools

In ToSC’20, a new approach combining Mix-Integer Linear Programming (MILP) tool and Constraint Programming (CP) tool to search for boomerang distinguishers is proposed and later used for rebound attack in ASIACRYPT’21 and CRYPTO’22. In this work, we extend these techniques to mount collision attacks on $$\textsf{SKINNY}$$ -128-256 MMO hashing mode in classical and quantum settings. The first results of 17-round (and 15-round) free-start collision attack on this variant of $$\textsf{SKINNY}$$ hashing mode are presented. Moreover, one more round of the inbound phase is covered leading to the best existing classical free-start collision attack of 19-round on the $$\textsf{SKINNY}$$ -128-384 MMO hashing.