This page is about around the theory of authentication, not actual authentication mechanisms as exposed by software systems.
The three authentication factors:
- Something you know, such as a password or PIN.
- Something you have, such as a credit card or hardware token.
- Something you are, such as a fingerprint, a retinal pattern, or other biometrics.
Authentication strength:
- One authentication factor is considered as weak authentication.
- More than one authentication factor is considered strong authentication.