At 17:30 -0400 9/6/00, juzam wrote:
according to applied cryptography, these permutaions do not effect the security of the algorithm, but i'm not sure about the purpose.
As I recall the basic purpose was to make it slow in software meaning that software cracking apps were/are at a severe disadvantage vs. hardware implementations. It would be interesting to see how much longer that extended DES's effective lifetime. I would consider the initial permutations to be in the same category as Blowfish's (and derivative algorithm's) time consuming key expansion phase- a neat "trick" that does not improve theoretical security but significantly increases the difficulty of real world attacks. -- Kevin "The Cubbie" Elliott <mailto:kelliott@mac.com> ICQ#23758827 _______________________________________________________________________________ "As nightfall does not come at once, neither does oppression. In both instances, there is a twilight when everything remains seemingly unchanged. And it is in such twilight that we all must be most aware of change in the air--however slight--lest we become unwitting victims of the darkness." -- Justice William O. Douglas