A Course in Mathematical Cryptography

3 Cryptanalysis and Complexity

3.1  Cryptanalysis and Cryptanalytic Attacks

As explained in Chapter 1, cryptology has two parts: cryptography and cryptanalysis. Cryptanalysis is the part of cryptology that involves the methods used to break a code or to attempt to break a code. By breaking a code or cryptographic protocol, we mean the ability, under appropriate assumptions, to either determine the secret key or determine the plaintext from the ciphertext without finding the key.

An attempt to break a code is called an attack. The security of a cryptographic protocol depends on its ability to withstand attacks. The person mounting an attack is called an attacker or an eavesdropper. It is common practice to call the communicating parties Bob and ...