> The Data Encryption Standard (DES) has constants that were given out by NSA. They turned out to be far from random, but instead made the algorithm resilient a

> The Data Encryption Standard (DES) has constants that were given out by NSA. They turned out to be far from random, but instead made the algorithm resilient against differential cryptanalysis, a method not publicly known at the time. The counterexamples are more interesting than the examples!