How are the permuted choice tables - PC-1 and PC-2 - calculated for the DES block cipher algorithm?
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Maarten Bodewes
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maryamjafari
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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. – Maarten Bodewes Aug 01 '18 at 13:13
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1See https://crypto.stackexchange.com/a/1684/ (one of the group's very first questions!) – dave_thompson_085 Aug 02 '18 at 02:44
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This seems a duplicate of DES Key Schedule Algorithm. – Aug 20 '18 at 20:34
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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.
BenM
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