Interesting. So it's a bit like providing a public key, if they need to make sure they are talking with you they ask you to provide the TOTP and they control they have the same number on their side?
Yeah that's right. So me, my 2 kids and my wife all have the same code, I have one with my brother and my dad (my mum is a bit too past it ... ) and one with my employees (I only have 2 ... ). It's like a way to prove you were all the same people in the room at the same time! I have a little script that produces a QR code, then I delete it and it will never exist again :) EDIT: my youngest daughter in particular really loves it. When I go on a run and get home without my key, and I knock on the door she grabs her iPad and opens the door a little crack and says "what's the code?"