Everywhere on the internet, it is found that the 58th bit position takes first position in initial permutation. Also, the 40th bit position takes first position in final permutation. Is this always the same in every case? I mean is this done randomly or in a particular order (the same order)?
1 Answers
Ciphers doesn't work randomly. In the case of DES, the tables (PC1, PC2, IP, E, P, IP-1, but also the shifts and the S boxes) are always the same. You can find them in Wikipedia; here's NIST official documentation. This documentation also contains a lot of test sets to validate correct DES implementations (with a small error... I challenge you to find it out!).
Anyway, this is another useful resource to fully understand DES.
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