How U2F works

I bought a Yubico security device from Amazon. This is the little piece of plastic shown here. I didn't understand how it works, and no one has ever explained it to me. Yubico has no technical support.

I followed the instructions on the Yubico site, that could not have been easier. I got an email from Google saying that 2-Step Verification had been turned on. Great! what did that mean?

I finally figured it out - and I should get a Purple Heart, or something for this effort. It works like this:

When you go through the installation, if it is successful, it establishes the following processes on your Laptop and your Phone.  Once that is done, you no longer need the little dongle.

When you turn on your laptop, you enter your password - same as before. It then sends a message to your phone. Your phone then replies, with a right message. Your laptop receives the message, and boots up, same as before. If your Phone is not working, your Laptop will not work either.

The whole things depends on two independent devices working together - your Laptop and your Phone. Really clever - but all this happens without the user knowing all this black magic is protecting him.

Even if someone steals your phone, but it is still working, somewhere else - your laptop will work.