So what happens if you lose a trusted device? Or maybe it crashes, or the user signed-in with incognito originally, or anything like that? What's the recovery mechanism?
For apps that prefer lower security, higher convenience, then possibly users can fall back to SMS OTP. For apps that require higher security, the app can revoke the lost device and either delete the account, or go through customer support to verify the user's identity and enroll a new device.
If you have 2 trusted devices and lost one, you can revoke access from the lost device.
Incognito shouldn't affect this because the trusted device works in mobile apps, not websites.
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.