Hi,
The ways in which someone may be authenticated fall into three categories, based
on what are known as the factors of authentication: something you know,
something you have, or something you are. Each authentication factor covers a
range of elements used to authenticate or verify a person's identity prior
to being granted access, approving a transaction request, signing a document or
other work product, granting authority to others, and establishing a chain of
authority...
security http://www.visual-guard.com/