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What is this? And tell me about what are rows when selected 1st and last bit???

  • $\begingroup$ I'm not sure I understand what you're asking… and if I do, the question might be a bit too broad. So, to clarify — can you please explain what exactly you don't understand? $\endgroup$ – e-sushi Oct 4 '17 at 4:30

S-box stand for substitution box. For every possible 6 bit input we replace with 4 bit output. For visual convenience the input is broken up into 4 bits and 2 bits. Giving a 4*16 matrix in each cell we have the 4 bit output for the input designated by that row and column. The 4 bits are the original bits and the 2 bits are from the expansion copied from neighboring 4 bit blocks.

We now know the DES cipher was designed to be resilient to differencial cryptanalysis which IBM and the NSA new of a whole 16 years before Eli Biham reinvented the technique and told the world.

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