Authentication
From Erights
Definition
Given one end of a communication channel, authentication procedure establishes which principal is probably at the other end.
Examples
Banknotes, for example, can also be viewed as "one end of a communcation channel". Banknote states that its holder has certain amount of money. Banknotes are valid, if that statement is claimed by the central bank. Authentication of the banknote reveals whether this is the case.