A smart card is a credit card sized device that contains a tamper proof computer chip. When it is used for security, this chip can hold and protect various types of credentials that the bearer can use for authentication. Smart card authentication requires a card reader.

Smart cards, like tokens, were developed for strong or two-factor authentication. So in addition to swiping the card to prove ownership of the credentials contained on it--something he has--the owner usually has to enter a PIN or password--something he knows.

The infrastructure to support smart cards must include a method to securely write the credentials to the card, usually a dedicated a computer and an application with administrator-only access to the server. Administrator access is often supplied with a “mother card”.

The advantage that smart cards have over tokens is that the memory chip can hold more information: separate credentials for multiple applications or for different authentication methods, for example.