hotp - Robuta Search

https://mojoauth.com/products/hotp/

Implement secure HMAC-based One-Time Password (HOTP) authentication with MojoAuth. Counter-based OTP solution for enhanced security.

https://ubuntu.com/server/docs/how-to/security/two-factor-authentication-with-totp-or-hotp/

Implement TOTP/HOTP two-factor authentication on Ubuntu Server using time-based or HMAC-based one-time passwords with public keys.