One Time Password (OTP)

One-Time Password (OTP) is a password that is only valid on a computer system or other digital device for a login session or transaction. It is also known as one-time PIN or Dynamic Password. OTPs related to static password-based authentication avoid a number of errors; Several implementations also ensure dual-factor authentication to ensure that a person needs access to something as well as something a person knows (such as a PIN).

The most important advantage addressed by OTPs is that unlike static passwords, they are not risky for resuming attacks. This means that a potential intruder who is able to record an OTP that was already used to login or trade a service will not be able to abuse it, as it will no longer be valid.  

Users who use the same (or similar) passwords for multiple systems are not at risk for all of them, if the password is obtained by an attacker, one of them. A number of OTP systems have noticed that no session can be easily interrupted or disguised without knowing the unexpected information created during the previous session, thus further reducing the surface of the attack.