This code appears to have only cursory resemblance to Bruce Schneier's blowfish and twofish algorithms in that it too has a table-based decoder. Derivation from FairKeys code by Jon Lech Johanson at nanocrew.net. If you don't know what that is, don't bother looking here further. This is a Pure Perl implementation. I doubt there is any need for xs coding for what would mainly be processing 16 bytes at a time. This code is part of an ongoing effort to clone portions of the Apple iTMS in Perl for portability. See www.hymn-project.org for prior efforts by others. WWW: http://search.cpan.org/dist/Crypt-AppleTwoFish/