Cryptanalysis of Grindahl.

Due to recent breakthroughs in hash functions cryptanalysis, some new hash schemes have been proposed. GRINDAHL is a novel hash function, designed by Knudsen, Rechberger and Thomsen and published at FSE 2007. It has the particularity that it follows the RIJNDAEL design strategy, with an efficiency comparable to SHA-2. This paper provides the first cryptanalytic work on this new scheme. We show that the 256-bit version of GRINDAHL is not collision resistant. With a work effort of approximatively 2^112 hash computations, one can generate a collision.