There are multiple ways to authenticate using more than one method. Most authentication methods rely on knowledge factors like passwords, while two-factor authentication adds a possession factor or an inherence factor. A vast majority of two-factor authentication methods rely on the first three points from the list. - Knowledge factors are those which a person can remember, such as a password or a PIN. - Possession factors are those a user has, like an ID card or a smartphone, or any other device. - Inherence or Biometric factors are factors from the user’s physical self. They may be a fingerprint, facial, or voice recognition. - Location factors use the location from where an authentication attempt is being made. Here IP address and GPS data are being used. - Time factors restrict a user’s authentication to a specific time window in which logging is permitted while restricting access to the system outside that window.