The Initiative for Open Authentication (OATH) is responsible for developing two standards - TOTP (clock-based) and HOTP (counter-based). Both are used extensively nowadays.
The Yubikey can emit an HOTP token when touched. For TOTP, a companion application (Yubico Authenticator) must be used as Yubikeys do not have an internal clock.
Why use a Yubikey for OATH?
- The shared secrets are stored securely in the Yubikey.
- Can be used on any computer and thus is not conditioned by typical mobile device issues, such as drained battery.