As a result, we are able to build complex non-linear differential characteristics for reduced versions of the hash function Skein. We present several characteristics for use in various attack scenarios; this results in attacks with a relatively low complexity, in relatively strong settings. In particular, we show practical free-start and semi-free-start collision attacks for 20 rounds and 12 rounds of Skein-256, respectively.
To the best of our knowledge, these are the first examples of complex differential trails are build for pure ARX designs. We believe this is an important work to assess the security of ARX designs against differential cryptanalysis. Our improved tools will be publicly available with the final version of this paper.Category / Keywords: secret-key cryptography / Symmetric ciphers, Hash functions, ARX, Generalized characteristics, Differential attacks, Skein Date: received 26 Nov 2012 Contact author: gaetan leurent at uclouvain be Available format(s): PDF | BibTeX Citation Version: 20121128:172453 (All versions of this report) Short URL: ia.cr/2012/668 Discussion forum: Show discussion | Start new discussion