pam_double_otp is a PAM module for adding HMAC-based one-time passwords (HOTP) according to RFC 4226 or time-based one-time passwords (TOTP) according to RFC 6238 to implement two-factor (2FA) authentication.

To increase security, the module requests two successive numeric one-time passwords (codes) consisting of 6 to 8 digits each. Only after successful authentication, there is the possibility to authenticate with a single one-time password (as second factor) next time.



  • 2019-11-11: Version 0.1.2
    • Code cleanup
  • 2019-11-09: Version 0.1.1
    • Improved README file
  • 2019-11-08: Initial release of version 0.1