CDR: Re: Permutations in DES
Kevin Elliott
k-elliott at wiu.edu
Wed Sep 6 18:08:07 PDT 2000
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 at mac.com> ICQ#23758827
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