In addition to user ID / password authentication, I also wish the authentication function with the confirmation code mailed. (So-called two-step authentication)

After logging in with the user ID and password in the Web UI, send the confirmation code to the user's mail address.
The user can not login without entering the code in the UI.
Make screen transition similar to input of confirmation code when logging in to WCA from new IP address.
The administrator turns ON / OFF this setting in the user account setting of the Web UI.