There is a way to implement proof of age that respects both speech and privacy rights. It's just not on offer.

In a sane country, you could do it with public key cryptography.

1. You digitally sign a statement that you are (let's say) over 18 years old, using your private key.

2. You carry that statement to the nearest post office, where the clerk checks some kind of government age ID like a drivers license. No record is kept, they just verify your age statement is true.

1/3