I wonder if not private age verification could not be solved with the right cryptographic protocol.
You would have to register using a digital ID with a government agency, to get a age certificate. Most European countries already have digital IDs, used for all sorts of things: such as taxes, online banking etc.
Then that certificate could be used in some sort of challenge-response protocol with web sites to verify your age, creating a new user ID in each session but without divulging anything that identifies that particular certificate.
I'm afraid that the alternative would be that social media would instead require login with the digital ID directly.
You would have to register using a digital ID with a government agency, to get a age certificate. Most European countries already have digital IDs, used for all sorts of things: such as taxes, online banking etc.
Then that certificate could be used in some sort of challenge-response protocol with web sites to verify your age, creating a new user ID in each session but without divulging anything that identifies that particular certificate.
I'm afraid that the alternative would be that social media would instead require login with the digital ID directly.