It can't be solved, but you can choose different loopholes and privacy trade-offs. Untraceable-but-single-use proof-of-age tokens? Good for privacy, but now th

It can't be solved, but you can choose different loopholes and privacy trade-offs. Untraceable-but-single-use proof-of-age tokens? Good for privacy, but now that 14-year-old can get tokens from an 18-year-old friend for cash. Proof tokens that only last a few minutes, or a three-way handshake between user, government and website? Harder to trade, but now the government's got a good guess about who's opening pornhub. Requiring sites to keep audit records, to prove they really did the verification procedure? Wildly insecure, we don't want them storing passport photos. Requiring them to not keep audit records? Then they can skip or half-ass the checks. Camera-based age estimation? Once again the 14-year-old can have an 18-year-old pass the check for them. Or a video game character creator or something. Scanning a government ID card? Better hope Dad never leaves his wallet unattended for 5 minutes. And not everyone has a passport or driver's license. Age attestation from an electronic driver's license, plus face id biometric validation, with a secure element, trusted execution environment and code attestation? Congrats, now you've handed your national ID database to the world's largest adtech/tracking company. Hope you weren't trying to distance your nation from US tech dominance.