Authentication
Authentication is the act of identifying an entity. In our case, authentication usually relates to identifying a person. The current method of authentication is by using a username and password. Since, passwords are complicated and are hard to type on a small device, phone number and PIN are used for authenticating a user.
Two-factor authentication
The most common approach today is two-factor authentication. This is based on the theory that to identify a person uniquely, a person should provide two of the following three identifiers:
Something that a user has; this includes a digital signature, security tokens, phone, tag, and so on
Something that a user knows; this includes passwords, secrets, PIN, or an answer to a question that only the user is expected to know
Something that a user is; examples include retina scan, fingerprints, and facial recognition
An example of two-factor authentication is logging in by using username/password or phone/PIN followed by entering a secret code...
