The most commonly used biometrics are fingerprints, hand geometry and retinal scans. Some examples of emerging biometrics are facial and vein patterns.
In order to be used for access control, the physical patterns of a biological characteristic – such as a fingerprint – are scanned and digitally mapped. The resulting code is stored in a database or on a Smart Card. When a person approaches a door or computer in order to gain access, their fingerprint, hand, etc, is again scanned and the results are compared to the stored code.