Two-factor authentication (2FA) is the security authentication method that requires two pieces of predetermined evidence (factors) before being granted authorization. 2FA is a subset of multi-factor authentication (MFA), the difference is the number of factors. Simply two layers of security required before a user can access an account or system. The most common examples of authentication factors used are passwords, PINs, hardware tokens, and biometrics.

There are five different types of authentication:

1) Possession factor - something you have

• Hardware token
• Software token
• ID Badge
• OTP token

2) Knowledge factor - something you know

• Password/Passphrase
• PIN
• Touchscreen swipe

3) Inherent factor (biometrics) - something you are

• Fingerprint scan
• Facial scan
• Vein scan
• Voice recognition

4) Location factor - somewhere you are

• Geography (geo-location)
• IP Address
• Local proximity

5) Behavioral factor - something you do

• Handwriting style
• Typing speed
• Movement dynamics
• Motion sensors