Authentication

Authentication is the process of determining whether someone or something is, in fact, who or what he declares to be. The most common example of authentication protocol is the use of username and password, where the knowledge of the password is assumed to guarantee that the user??™s claimed identity is valid. Usually, authentication is based on one of the following three factors: something the user knows (a PIN or a password), something the user has (e.g. a smart card or token), and something the user is (physically; e.g. finger prints or retina scan). Two-Factor Authentication refers to the act of requiring two out of the three previously listed authentication factors. The best known example is the act of withdrawing funds from an ATM machine, which requires both something the user has (the ATM card) and something the user knows (the PIN number).