For SSH, use native U2F/FIDO2 OpenSSH support instead: https://www.openssh.com/txt/release-8.2 https://www.openssh.com/txt/release-8.2 https://cryptsus.com/bl

For SSH, use native U2F/FIDO2 OpenSSH support instead: https://www.openssh.com/txt/release-8.2 https://www.openssh.com/txt/release-8.2 https://cryptsus.com/blog/how-to-configure-openssh-with-yubikey-security-keys-u2f-otp-authentication-ed25519-sk-ecdsa-sk-on-ubuntu-18.04.html https://cryptsus.com/blog/how-to-configure-openssh-with-yubi... TOTP with a PAM module is insecure since it's not cryptographically tied to the session like public key auth and can be phished. The author's suggestion to use it for passwordless login is dangerous when applied to SSH sessions!