I'm curious about the design of the P_BOX of DES. I found a paper on this topic, but it dates back to 1989. This means the effect of p-box values of the cipher immunity against Differential Cryptanalysis and linear cryptanalyisis is not mentioned since they were Publicly discovered during the 90's (According to Bruce Schneier's book "Applied cryptography , the NSA and IBM knew about the attack since the 70s). I tried to look online, but it seemed to me that unlike the S-boxes which have considerable amount of literature, there are no good resources on the p_boxes.
The placement of the p_box in the Feistel function is shown here:
The permutation itself is shown here:
Previously on Crypto.SE, we explored the roles of the initial and final permutations and how they impact security. What about the permutation in the Feistel function? What impact (if any) does it have on security?