Comment by Grimeton
2 days ago
They could just issue a x509 cert with an above 18 attribute and nothing else.
You're not 18 yet?
No Problem we just give you two certs with different valid from/to ranges that overlap and don't give away your birthday.
Problem solved.
Steelmanning the opposing position: one adult shares their certificate with every child on the planet.
Because it has no attributes (not even a unique serial number that could be used to track it) the whole scheme is now defeated.
Which, adult is merely someone who's just turned 18. What're the chances that any of them just post the thing up on 4chan? (I'm going to go with 100% chance of that happening.)