Just offer the user some money if he installs some "trusted" app for age verification token sharing.
Mobile devices are secure and that’s why they’re not infected with malware, like any Windows machine. This is why Android is the host of 98% of all mobile malware and iPhone is not.
You have the freedom to make your own insecure devices which don’t have any trusted or secure elements. Go for it! Take your GNU and go wild.
The internet has plent, of security elements. Devices use TLS to communicate, are encrypted by disk encryption, users' messages/calls/data are encrypted with various protocols... This is already in place.
Building codes and such are laws, the government didn't go and change the laws of physics to make it impossible to build something not up to code. They also don't limit the same of materials and tools to only certified builders who they know will respect the code. You can still break the rules to some extent, or even follow them, just without external certification.
Remote attestation and related technologies change the laws of physics - not complying is simply not possible. You can't just make one little change and hope nobody bothers you about it, the system makes the change impossible, or it detects it and "burns the whole house down".
If your house isn't certified because you repaired a light fixture on your own, you can still invite friends over, you can receive mail and packages to it, you can get phone, internet and other utilities. If you want to change the color of the icons on your phone, or if you want to disable the pre-installed spyware, you're cut off from talking to your firends and family, from social networks, reading the news, you can't pay your taxes, can't get a bank account, can't get paid for your work or even apply for a job. That is the reality we're going towards.
The thing that changes isn't that your every action will be followed. That already happens. It's that you are powerless to avoid it. It's a technological lock to keep you obedient. There is no security element to it. We as an industry need to stop pretending like these are security technologies and start talking to more social sciences experts. Before it's too late...
If there's a simple piece of software that can be installed, it's not meaningfully increasing the barrier. Also, there are negative consequences to introducing "rules that you're expected to break" like this. It makes the law unserious.
And if it's a phone app, it's not going to be on app stores and you already know the person giving you the app is a criminal.
So you're installing an untrustworthy app to risk criminal charges, and the customers of this scheme are kids who mostly don't have a lot of money.
So the schemes inherently add some traceability, which makes the tokens no longer actually anonymous.
This is the back door used to make the tokens double as ID tokens.
1) You give a teenager your full credentials. Teenager is careless, as teenagers often are, and posts something revealing who he is. Cops have option to search teenager's phone, see who you are, and at least revoke the credentials.
2) You install a relay app on your phone, for money. Now you've installed an untrustworthy app from a criminal, who might hack you, or might be arrested and reveal details of your device and where they're sending your money.
Neither scenario happens because the age verification is traceable.
3) Your credentials get stolen, and used in a foreign country to implement a relay scheme.
This one, I admit, my scheme can't do anything about. But this means our teenager has to pay a foreign entity. Teenagers can also pay foreign porn sites directly, if porn is our concern.
On top of that, the age verification systems we've seen so far have their own security holes that teenagers are exploiting without having to pay anything.
My personal view is that the whole thing is ridiculous and we shouldn't bother with any of this. My point is just that we can implement reasonably good age verification without eliminating anonymity on the internet.