[andrepd]

All states/governments have basic records on their citizens and residents, including at least a name, dob, address, etc, at least for a passport, driver's license, if not an actual id card. Let's assume this is acceptable.

Then it's technically possible (and really not that difficult) for states to provide a service that issues zero-knowledge proofs of facts like "age > X".

[AdrianB1]

> Let's assume this is acceptable.

(partly off-topic rant) One can argue this is a false premise fallacy. For most of the time states did not have this information about their citizens and the world progressed quite nicely. The only argument to know stuff about citizens that don't drive (increasing numbers) nor travel abroad (different problem altogether) is to tax them?

One of the foundational differences between humans and cattle was you cannot brand (https://en.wikipedia.org/wiki/Livestock_branding) humans. Not physically, because we do it digitally and I see a slippery slope.

[andrepd]

The discussion was about age verification, not about the (rather more extreme) position that it's illegitimate for the state to hold information about its citizens.

> For most of the time states did not have this information about their citizens and the world progressed quite nicely.

This is quite untrue. State bureaucracies far predate the modern era.