A FIDO U2F Security Key is an open authentication standard that strengthens and simplifies two-factor authentication using specialized USB or NFC devices based on similar security technology found in smart cards. U2F Security Keys are currently only supported by Google Chrome since version 38 and Opera since version 40.
If you choose the “FIDO U2F Security Key” option, the next screen will prompt you to insert your security key into the USB port on your computer. This will register the device with your ID.me account and the 2-factor authentication enrollment process will be complete.
If you to add the additional layer of security with 2-factor authentication, you will see a screen confirming that you’ve completed the enrollment process.