In the 35 years we’ve had personal computers, tablets and smartphones, authentication has meant a username and password (or Personal Identification Number, PIN) for most people. Yet other methods, and other schemes for using those methods, have been available for at least the past 30 years. As we look to replace ─ or at least augment ─ passwords, it’s time to re-examine these methods and schemes.

Multi-factor refers to using at least two of the three generally agreed authentication methods: something you know; something you have; and something you are.

Something you know: the most widely used factor because it includes passwords. It refers to what is called a “shared secret” ─ something known to the user and the system they are authenticating too. Also included in this are PINs, pass phrases, security questions, etc. Security questions come in two types: those previously configured (mother’s maiden name, first car, city of birth, etc.) and those the authenticator gleans from public records (usually multiple choice, such as “which was your address when you lived in London” with one choice being “I never lived in London”).

Something you have: usually a token of some kind. The RSA SecureID is, perhaps, the most widely known but there are lots of others. Proximity cards, for example, or your smartphone could be one. In one scenario, you log in with a username and password and the system sends you a code via text to your phone. You then enter that code to complete the authentication. Note that the US National Institute of Standards and Technology (NIST) has just deprecated the use of SMS messaging as a second factor due to security issues.

Something you are: usually a biometric of some type: fingerprint, retina scan, facial scan, etc. It can also be a measure of your typing, swiping ─ or even walking! Handwriting is also included, but is now mostly just a subset of swiping. Other, more exotic schemes include palm scans and vein readings.

Any of these can be used for authentication. For a stronger system, you would choose one each from two or all three groups. Two types from the same group (say a password and a PIN or a PIN and a security question) does not constitute a multi-factor authentication.

Dynamic, or adaptive, authentication involves having the system check the context of the login (who is it, where are they, what platform, etc.) and deciding which factor or factors (and which methods of those factors) should be applied in the given situation. This is an essential element of risk-based access control.

Finally, there’s continuous authentication. Passwords could be requested periodically (irritating to the user) or the presence of a proximity card could be detected periodically (and the session timed out if it’s not present) or the keyboarding could be constantly checked against the user’s baseline and the session timed out or the user asked to input something they know so that the session can continue.

We recommend that you look into adaptive and/or continuous authentication as an integral part of your access control system.