# Tag Info

Each one of your first two sentences has a mistaken premise: you're starting from some assumptions that aren't actually true. DES does not use small PRPs for saving memory. It doesn't use small PRPs at all. The DES S-boxes are not PRPs. The DES F-function is not a PRP. A PRP does not necessarily require $\lg(2^n!)$ memory. Actually, most PRPs have ...