How are the permuted choice tables - PC-1 and PC-2 - calculated for the DES block cipher algorithm?

  • $\begingroup$ I think they were established rather than calculated. Note that the DES / Lucifer cipher wasn't part of an open competition where cryptographers discussed their algorithm freely. So not all design rationale may be known - hopefully somebody can answer this one. $\endgroup$ – Maarten Bodewes Aug 1 '18 at 13:13
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    $\begingroup$ See crypto.stackexchange.com/a/1684 (one of the group's very first questions!) $\endgroup$ – dave_thompson_085 Aug 2 '18 at 2:44
  • $\begingroup$ This seems a duplicate of DES Key Schedule Algorithm. $\endgroup$ – user1430 Aug 20 '18 at 20:34

These are not calculated, but as with the particulars of S-boxes, suggested and reviewed as part of the design.

These fixed values/configurations are intended to add certain qualities to the particular step of each round, essentially obscuring the final output as much as possible, in a non predictable way. As you can read on Wikipedia, there is some controversy involved in the development of the S-boxes.

There was some criticism from various parties, including from public-key cryptography pioneers Martin Hellman and Whitfield Diffie,[1] citing a shortened key length and the mysterious "S-boxes" as evidence of improper interference from the NSA.


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