Two-Factor Authentication

A system identifies a user through a user identifier, commonly abbreviated to user ID. The process by which a system confirms that a user really is who the user claims to be is called authentication. We saw in Chapter 5 that there are three types of credentials through which a user can be authenticated: knowledge factor (what a user knows), ownership factor (what a user owns), and inherence factor (what a user is).

When you have an authentication mechanism that leverages a combination of two of these factors, it is called two-factor authentication (TFA, T-FA, or 2FA). A real-life example for TFA is an automated ...

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