The google authenticator project includes implementations of one-time passcode generators for several mobile platforms, as well as a pluggable authentication module (pam). one-time passcodes are generated using open standards developed by the initiative for open authentication (oath) (which is unrelated to oauth).

these implementations support the hmac-based one-time password (hotp) algorithm specified in rfc 4226 and the time-based one-time password (totp) algorithm currently in draft.