I mean, doesn’t somebody still need to validate that those keys only get to people over 18? Either you have a decentralized authority that’s more easily corrupted or subverted or else you have the same privacy concerns at certificate issuance rather than at time of site access.
The point would be, to roll it all into the ID issuing process. I think most EU IDs already have cryptographic identities built in. The certificate issuing should probably be a state service as well. The alternative would probably be, just mail your birth certificate and a 3D scan of your anus to the private age verification provider of your choice.
It of course all falls back to a central state authority. But the process wouldn’t have to be more centralized and privacy-invasive than state IDs already are. Control of resident data could be kept at municipality level, and you wouldn’t need a central approver, that gets a running feed of all my age-restricted activities.
Before I sound like I’m soying over ID verification, I’ll add that all this junk can become insidious very quick, if it becomes easy to implement and gets used everywhere. I also detest beyond measure that my ID currently stores a scan of my fingerprint, and I hope the court-ordered deadline makes that shit illegal again in 2027.