2.2 Preliminaries
The fundamental objective of cryptography and computer security in general is to enable two persons, let’s call them Alice and Bob, to communicate over an insecure channel so that an opponent, commonly called Eve, cannot understand or unnoticeably alter their messages [168]. Alice, Bob, and Eve can also be referred to as (communicating) entities or parties and may be people or machines. Alice and Bob are either a sender or receiver, that is, a legitimate transmitter or intended recipient, of the messages. Eve is an adversary, an entity that tries to compromise the information security between Alice and Bob.
Figure 2.1: Legitimate communicating parties Alice and Bob transmit and receive information over an untrusted channel
Let’s clarify terms by looking at some definitions:
An insecure or untrusted channel is a channel an opponent, or attacker, can access. The capabilities of the attacker (that is, what the attacker can or cannot do on the...