Good day all, I am building an app in flutter and I use firebase as the backend. I allow users register and sign into the app using their phone number (and then a password). However, I want to add an extra layer of uniqueness to the registration/login flow.

What I mean is that, I only want one a maximum of one account to be reachable from one device. If person A creates an account on phone A, they can only ever use the app from phone A. Person A should not be able to log into their account from phone B.

I do not believe an sms two factor is enough for this because person A can share the two factor code with person B. Person B would then be able to login to Person A's account on phone B because they have person A's phone number and 2 factor code.

Is there a way of implementing this for a flutter app running on firebase?

CodePudding user response：

You can try saving the unique device ID of the user upon registration then you can check on login whether the user is on that specific device. For getting the unique device ID, you can check here.