> my main point of contention with you is that in your threat model, a lost phone is a security problem, yet a lost u2f is not I realized that I could explain

> my main point of contention with you is that in your threat model, a lost phone is a security problem, yet a lost u2f is not I realized that I could explain my concerns better in the article. My biggest issue with the phone is not that it could get hacked, but that I could just lose it together with my u2f token (because, you know, I always carry both phone and u2f token), and thus get myself locked out of my accounts. So it's not about somebody attacking me specifically to get my 2fa data, but just about some bad luck happening which results in losing both u2f token and a phone which was a backup for u2f token. Instead of Google Authenticator we could use Authy, which synchronizes its database with the server, but Authy account could be recovered with SMS, which is anything but secure. I actually updated the article just now with that point. I really want having a backup which is rock-solid secure and reliable, you know, more reliable than any other 2nd factor I have. So having a token bricked into the wall or something like that would work. > you need to revise your threat model or revise your solution When I have a chance to reimplement the same backup concept having something more secure than u2f-zero, then yeah I surely will revise the solution.