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Security Education Companion
A free resource for digital security educators

One-time password

Passwords are usually semi-permanent: once you set them up, you can keep using them until you manually change or reset them. One-time passwords only work once. Some one-time password systems work by having a tool or program that can create many different one-time passwords, that you use in turn. This is useful if you're afraid that there may be a key-logger on a system where you have to type in a password.