Erin Alexis Owen Shepherd


Permutations: Replacing the block cipher?

History For the past few decades, the block cipher has been the primary symmetric cryptographic primitive. Aside from the odd stream cipher (primarily RC-4), pretty much every common cryptographic primitive from before 2010 can be seen as built from a block cipher. Quick note: How do we define a block cipher? A block cipher is a function with the form c = f(p, k) where c, p are an N-bit ciphertext and plaintext respectively, and k is an M-bit key.