alt Hacker NewsThe EU actually has a very good, privacy protecting way of doing this based on zero knowledge proofs.
Unfortunately they completely botched it by having the proof-of-concept app rely on Apple & Googles integrity APIs - which a bunch of countries copied.
ZKPs may as well just be unencrypted HTTP headers which would be way simpler and easier to implement. All a ZKP proves is that at least one person in the world is over 18.