Seems sensible. Interestingly, there's no persistent unique identifier on a UK passport (short of the personal details, which will be unique). But there's no SS

Seems sensible. Interestingly, there's no persistent unique identifier on a UK passport (short of the personal details, which will be unique). But there's no SSN or equivalent on them, and no address. Passport number is a relatively infrequently used thing, on account of the fact it changes on any renewal or replacement. If you have two passports, they have two different numbers. Having a "non-ID" culture is a nice thing though - in the US, people need to show ID to board even a domestic flight. Having an app to help redact ID is a nice idea, but in my view is a fairly poor solution to a non-technical problem. If you didn't insist on having these places collect ID info, you wouldn't need the app. For proof of age, that's a good scenario where you likely do need ID (today), but in future should be able to use attribute-based authentication to pove this without disclosing anything.