ABSTRACT
The 1970s also saw a revolutionary change in the manner in which cryptographic keys were handled. Cryptography was about to go public. In order to begin to describe the ideas behind this approach, we need some terminology. In what follows, when we speak of an entity we will mean any person or thing, such as a computer terminal, which sends, receives, or manipulates information. Also, when we speak of a channel we will mean any means of communicating information from one entity to another. A secure channel is one that is not physically accessible to an adversary, whereas an unsecured channel is one from which entities, other than those for whom the information was intended, can delete, insert, read, or reorder data. Now let us have look at how this idea developed (some of which is taken from [64]).
