2FA (Two-Factor Authentication)
Two-factor authentication (also known as 2FA) is a method of confirming a user's claimed identity by using a combination of two different factors: 1) something they know, 2) something they have, or 3) something they are. Withdrawing money from a cash maching is a good example, where the user has a bank card (something they have) and a PIN code (something they know). An alternative is using a One-Time Password (OTP) to provide a single-use PIN or password that is generated by a device in the user's possession or sent to the user's mobile phone via SMS, email or push.
See Melrose Labs Identity and Location, Melrose Labs One-Time Password
Melrose Labs: Our mission is to deliver pivotal services in cloud communications across mobile, fixed-line and internet for enterprises of all sizes. Through these services, we help businesses and other organisations communicate better with their staff and customers, and by doing so increase their success.