I am releasing my collision generators for MD4 and MD5. They have significant time improvements over the ones described in the papers by Wang, et al. MD4 collisions can be generated almost instantly, MD5 can be generated in approximately 45 minutes on my p4 1.6ghz (on average). http://www.stachliu.com/collisions.html Enjoy -Patrick Stach PS. Please do not reply to this address.