Two factor authentication is a way to ensure extra security for your account. Apart from knowing your password you also need (a phone or a USB device) to login. Banks also use this for login or making a payment by sending you a TAN code or by filling in a code at a device.
At BL3P, two factor authentication is not a default setting for login (although we block logins from new locations), withdrawals have to be confirmed by e-mail. Although this provides extra security, it is not considered a true two factor authentication. That's why we advice to use Google Authenticator. This is an app that lets you use your phone as a two factor authentication device.
Download Google Authenticator here:
After downloading the app you can set up two factor authentication in your account at 'security'. You will see a QR code which you can scan with your phone from Google Authenticator.
We expect to support Yubikey as a two factor authentication method in the near future.