What is Authentication?

Checking that you really are who you claim to be is called authentication. It is the first gate of any secure system: before an application lets you in, it asks you to prove your identity.

Authentication is like showing your ID at the entrance of a club. The bouncer compares the face on the card with the face in front of him. If they match, you get in. If they do not, you stay outside. Software runs the same check, just with different kinds of proof.

The Three Kinds of Proof

Systems verify identity with three categories of evidence, called factors:

• **Something you know