Block Ciphers and Modes of Operation
Most modern private-key encryption schemes are built from two ingredients: a block cipher and a mode of operation. Block ciphers are cryptographic primitives that provide encryption and decryption functions which operate on strings of a fixed size (blocks). The modes of operation act on top of block ciphers and allow the encryption of arbitrary length messages and also provide the probabilistic encryption necessary for the system to be secure. In this chapter we are going to look at these constructions and, in particular, at the most used block cipher today: the Advanced Encryption Standard.