With this module you can assign a Yubikey to an existing admin user to increases the security. Every user with assigned yubikey must enter a one time password generated by Yubico Yubikey. After you assign a yubikey to an admin user the login is splitted into two login forms. The first is the standard form where you must insert your magento login credentials. The second form need a 44 character long one time password which will be generated by pressing the button on your yubikey. The one time password will be validated by an authentification server. A user can only access the magento backoffice if username, password and the one time password are match.