Great!

Plugins works fine with WP 3.9 and it is a great addition to my other login protection plugins “Captcha” and “Limit Login Attempts” + htaccess for the wp-admin section ??

Would be great if the plugin could have a verification funtion with the first generated code to see if it works (just like other websites) and add a “Backup Code” just in case you do not have the secret key at hands or access to FTP to disable it temporarily.