If you want to actually enforce age restrictions that can be checked via some kind of digital identity I don't see how we can avoid the "trusted" hardware requirement.

The key material must be DRM'ed, especially if some ZKP solution is used.

Otherwise all underage kids would download the cool older brothers private key and load it into their GNU Taler client, buy wine and be gateway'ed into heavier Stallmanisms. Before soon EMacs would be all the rage in highschool.

(Of course we can argue the bigger points, if X should require age checks, or if this even should be done digitally etc. But there's a reason why we don't allow the physical equivalent of self-signed keys for physical ID's, they're not trustworthy)

Perhaps one could construct a bond-based system. It wouldn't help family collusion, but it would help limit people of age selling their authentication ability.

Say you have a public service and a platform site (social media, gambling, whatever), and the user does authentication in a way that anonymously proves to the platform that they're of age while revealing nothing else, and without revealing to the public service what platform they're accessing. But the protocol requires some expensive data (token that provides access to a bond account) which anybody MITMing the protocol can obtain.

Then if Alice tries to sell her age verification abilities to Bob, the protocol could be designed so either Alice learns the negotiated key and can snoop on everything Bob does, or she has to let Bob do a man-in-the-middle over a channel and lose the ability to observe what's going on after the first key exchange; and then Bob can acquire the token and make use of it at a later time.

This is very handwave-ish, but I don't think such a protocol would be impossible to design.

Under normal use, Alice has no reason to drain her own bond account. But if she's selling to an anonymous crowd who might use the token at any time (hence she can't trace the traitor), some troll is eventually going to do it.

> If you want to actually enforce age restrictions

I don't.

This "think of the kids" nonsense is a psyop to manufacture consent for this shit. People really need to stop falling for it.

Xkcd 538. Hardware attestation is not required because it's not sufficient, you need to plug all the other much easier ways to get around the system.

Firstly, you need to comprehensively ban VPNs, probably with some great firewall setup.

Secondly, you need to install CCTV in people's homes to make sure that nobody uses someone else's device to get around the system.

Then it's time for hardware attestation.

> I don't see how we can avoid the "trusted" hardware requirement.

While this is a good point, what's missing here is that this hardware doesn't have to have Google spyware and other bloatware installed. Yet with current design, this becomes mandatory.. security requirements are abused here to force unrelated software on my computer that I have to carry with me in order to participate in society.

This app should work on a dedicated device, something like a smartcard with e-ink display.. it would even be more secure because it would have less attack surface. Just like today I'm not complaining about not being able to install linux on my credit/SIM card, I'd not complain about that either. But locking down the whole OS on my smartphone is unacceptable.