CDR: Re: Permutations in DES

juzam juzam at cyberspace.org
Wed Sep 6 14:30:35 PDT 2000


according to applied cryptography, these permutaions do not effect the
security of the algorithm, but i'm not sure about the purpose.

Augusto Jun Devegili wrote:

> Hi all,
>
> I was just wondering... In DES, there's an Initial
> Permutation (IP) on the plaintext, then 16 rounds, and
> then the inverse permutation (IP^-1) of the result to
> produce the ciphertext.
>
> How effective are these permutations? Do they really
> add diffusion to the algorithm, considering that they
> don't depend on the key?
>
> Someone told me that they are necessary to provide
> reversibility to DES. Is this correct?
>
> Thanks in advance,
> Best Regards,
>
> Devegili

--
foo=====================
   rim vilgalys
  juzam at cyberspace.org

 -export-a-crypto-system-sig -RSA-3-lines-PERL

#!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj
$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1
lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)

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