> Using modern cryptography, it is easy to send a machine-generated proof to your social media provider that your government-provided ID says your age is ≥ 16, without revealing anything else about you to the service provider (not even your age), and without having to communicate with the government either.

There's just one problem. How does the machine proving your age know that you are who you say you are? Modern cryptography doesn't have any tools whatsoever that can prove anything about the real body currently operating the machine--it can never have such a tool. And the closest thing that people can think of to a solution is "biometrics," which immediately raises lots of privacy concerns.