One of the ways that a person can authenticate to a computer system or application is by using a small, portable hardware device called a hardware authenticator; sometimes called a security token.

Hardware authentication was designed to make strong authentication, also called two-factor authentication possible. So in addition to proving possession of the hardware device, a PIN or a password is usually needed. Proving possession of the device can be done in several ways, depending on the device. Some hardware authenticators are synchronized by time or event to a server and propose a one-time password that’s displayed on the device and can be used to prove possession. Others take a challenge code from the login system and present a new code to be used for login. And others simply plug into a USB port on the computer or mobile device.