U2F keys can be purchased online for the price of a cup of coffee. They’re being touted as the next best thing in online security authentication.

How do you know that the key that arrives at your doorstep is unique and doesn’t produce predictable or known output?

There’s plenty of opportunities for this to occur with online repositories with source code and build instructions.

Price of manufacturing is so low that anyone can make a key for a couple of dollars. Sending out the same key to everyone seems like a viable attack vector for anyone who wants to spend some effort into getting access to places protected by a U2F key.

Why, or how, do you trust such a key?

The recent XZ experience shows us that the long game is clearly not an issue for some of this activity.