OTP | One-Time Password
A one-time password (OTP) solution offers two-factor authentication using something you know – such as a pass code – combined with something you have like hardware token to generate an OTP. As their name implies, OTPs are only valid for one login session or one single transaction; they expire once they are used. They avoid many of the shortcomings that are associated with traditional static passwords, the most important of which is that OTPs are not vulnerable to replay attacks. In other words, even if an OTP is stolen, it can only be used one time.