CDR: Permutations in DES

Augusto Jun Devegili devegili at inf.ufsc.br
Tue Sep 5 16:55:50 PDT 2000


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





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