Multi-factor authentication aims to grant access to computer systems (e.g., Internet banking) using several pieces of evidence from the user, such as a knowledge factor, a possession factor, or an inherence factor.
|Knowledge||Logins, passwords||are the most common form of authentication. For PayPal, only a login name and password are necessary to make payments|
|Possession||Payment cards||Possession factors are the payment cards on which digits are printed on the front of the cards and CVC codes are written on the back. However, payment cards are becoming another knowledge factor because cardholders store their cards online.|
|Mobile phone||They are frequently used as possession factors, notably for 3D Secure where SMSs with passcodes are sent to cardholders.|
|Mobile apps||Applications also exist to generate security codes with momentary validity. Driven by open time-based one-time password algorithms; these are similar to the security tokens described above.|
|Security tokens||Online banking often uses tokens, small devices that help users prove their identities electronically, e.g., by storing cryptographic keys or passwords or by using small keypads and screens to authenticate users.|
|USB sticks||USB sticks also exist with embedded RFID chips. With the press of a button, a cryptographic string is sent back to authenticate the user; Yubico is one of manufacturer of such devices.|
|Inherence||Biometrics||Associated with the user, these include face recognition, fingerprint identification, retina scan, iris scan, and signature or voice analysis.|