Our product have 3 features:
- Cross-app phone number verification. The phone number is used only to check if the phone number is active. This is never used for authentication or logging in, and don't have anything to do with the Trusted Device. (For example, sometimes you would register to a website with email and password, and then somewhere in the flow they ask you to verify your email. This email verification has nothing to do with your password)
- Trusted Devices for authentication. The trusted devices are done using cryptographic keys that are generated upon registration. This keys are unique per app, per account, per device. No Cross-App trust here, we don't want any app to be reliant on any other app on authentication.
- Pin/Biometric as additional features.
So the cross-app is only for verifying the phone number. The trusted device is not shared across apps.