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.
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: