0

I'm learning DES, but I have a question.

When the plain text input, it gets a permutation by a table. Table

But, I don't know why 01 -> 58 / 02 -> 50. Is there any special rule or principle of it? or was it just set by the creator of DES?

fgrieu
  • 140,762
  • 12
  • 307
  • 587
AABAA
  • 1
  • That regularity comes from the initial implementation of DES in hardware: the plaintext was loaded sequentially as 8 octets, with at each of 8 loads each of the 8 bits of an octet entering an 8-bit shift register, 4 of which for L, 4 of which for R, with these 8 shift registers clocked simultaneously. A natural software implementations can mimic that (among other possibilities). – kodlu May 26 '21 at 02:52
  • 1
    possible duplicate see answer (partly quoted above) to https://crypto.stackexchange.com/questions/10542/how-is-the-initial-permutation-of-des-created – kodlu May 26 '21 at 02:53

0 Answers0