lang/en/settings.php

<?php
$lang["enable"] = 'Enable two factor authentication via Yubi Authenticator.';
$lang["validationServer"] = 'Adress of the server used to validate the Yubi Password';
$lang["clientID"] = 'Yubico Client ID used for the signature';
$lang["clientSecret"] = 'Secret used to validate the signature mentioned above, leave empty to disable validation';