Improve login security with challenge-response authentication

Technically, when you provide a password, you’re responding to a user name challenge. The offline challenge response covered here requires your user name first. Next, Fedora challenges you to provide an encrypted physical hardware token. The token responds to the challenge with another encrypted key it stores via the Pluggable Authentication Modules (PAM) framework. Finally, Fedora prompts you for the password. This prevents someone from just using a found hardware token, or just using a user name and password without the correct encrypted key.