CertiGuide to Security+  9  Chapter 1:  General Security Concepts (Domain 1.0; 30%)       9  1.2  Authentication

1.2.4  Username/Password 1 1.2.6  Multi-Factor

A token is usually a hardware device (most commonly assumed to be an RSA SecureID token-type device), which changes an ID code on a frequent basis, normally 60 seconds. Tokens are used to authenticate yourself via “something you have” and “something you know” – along with every SecureID token; you are issued a PIN number.

These SecureID devices are slightly smaller than a box of TicTacs, and have an LCD screen on the front. The screen displays a seeded number that changes every 60 seconds. When you connect to the server (normally via a VPN tunnel etc), you enter your PIN number followed by the number showing on your token. The server then authenticates you based on that, as the server has the same seed as your token, knows your PIN, and can therefore confirm that the two match. This complies with the "something you have and something you know" model.

The other way tokens are used in authentication is simply as data. On some systems, when you authenticate yourself, you are given a special set of data, known as a token, identifying you to the system. In the future during your computing session, when you need to furnish authentication information (for instance, to other network services), rather than sending the user and password again, you send this token data. Possession of this “virtual token” is proof of your authenticated identity.

1.2.4  Username/Password 1 1.2.6  Multi-Factor