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@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*',/((..)*)$/) =====================bar