The HOTP Toolkit package contains tools that are useful when deploying the one-time password HOTP technology. It contains a shared library, a command-line tool to generate and validate one-time passwords, and a PAM module (pam_hotp) to make system login or SSH use HOTP one-time passwords for authentication.
You can download it from the following link: https://packetstormsecurity.com/files/download/97123/hotp-toolkit-1.0.1.tar.gz
Source: https://packetstormsecurity.com/files/97123/HOTP-Toolkit-1.0.1.html