We must now digress from our discussion of the technology of cards and readers to cover another two sets of technologies that have a major impact on cards, and are likely to grow in importance in the coming years: biometrics and cryptography. This chapter will cover biometrics and Chapter 5 will address cryptography and the security of cards.

In most smart-card applications, the card is associated with a person; it represents a key to that person's details in a database. It is, therefore, very important to be able to identify the person who is using the card and to ensure that he or she is the person whose details are being unlocked. Often (for example in an access control or passport application), this is the main purpose of the card or application. In other cases the purpose is to allow access to data stored about that person.

In most card-based systems we need to do this automatically, although sometimes there is a human element as well (for example, inserting the card could call up an image of the card-holder, which can be checked while the user is entering his or her password or verifying a fingerprint).

Many people feel that a human check is better than any automatic check, however this is definitely not true when the population being checked is large.