What is a conventional encryption algorithm?
A conventional encryption algorithm is a function that maps an n-bit plaintext block to an n-bit ciphertext block where n is the blocksize. Typically, n is equal to 64 or 128-bits. The function takes a parameter, the “key” which specifies which mapping between the plaintext and ciphertext is used. Block ciphers are, given the same key, invertable. An excellent (and free!) introduction to block ciphers is the paper [Mir98].
