This paper deals with cryptanalysis of one hash function based on isotopy of quasigroups [J. Dvorský, E. Ochodková, V. Snášel: Hash functionbased on quasigroups, in: Proc. of Mikulàšska kryptobesídka, Praha, 2001, pp. 27-36. (In Czech)], [J. Dvorský, E. Ochodková, V. Snášel: Hash functionsbased on large quasigroups, in: Proc. of Velikonoční kryptologie, Brno, 2002, pp. 1-8. (In Czech)]. Our work enhances the paper [M. Vojvoda: Cryptanalysisof one hash function based on quasigroup, Tatra Mt. Math. Publ. 29 (2004), 173-181], where the simplified studied hash function, based only on the quasigroup of modular subtraction, was successfully cryptanalysed. In this paper we show how to construct collisions, 2nd preimages, and also preimages for the full hash function based on isotopy of quasigroups.
