3 ms·

I don't have the citation on hand right now, but if I recall correctly their recommendations strengthened DES against mathematical attacks, but weakened it agai

• gizmo686 13y ago
  I don't know what it means to weaken DES against brute-force attacks, but, if I recall correctly, their changes did weaken it against linear crypto analysis. Their change was to replace the random constants of DES's s-boxes with their own constants. They have since then published the criteria that they used to generated these constants. Based on the fact that everything I have read on the subject, and talking with several cryptographers, says that the change was to strengthen DES against differential crypto-analysis, I think it is reasonable to believe that this is supported by looking at how they generated the constants.
  • mnordhoff 13y ago
    NSA suggested decreasing DES's key size. IBM ultimately agreed to use effectively 56-bit* keys. This by definition makes brute force attacks easier. It was apparently criticized at the time, but it's worth noting that there's nothing secretive about it -- it's a basic and obvious element of the algorithm. The public cryptographic community started brute-forcing DES keys for fun in the '90s; with the NSA's budget, they could have been doing it from the beginning. * DES keys are 64 bits, but 8 bits are for parity, so the meaningful key length is 56 bits.
• wfunction 13y ago
  Yes, I just read this yesterday I think.