[notfed]

If you're going with a "digital id signed with government keys", then we don't need a ZKP, we can just use digital signatures. A certificate from the government that says "the holder of this id is 18+" is all the information that needs to be contained in the certificate.

[plastic3169]

That is a moving target. I could be 17 today and 18 tomorrow. Also it is not feasable to make all the different variations of ID but they do give out single one with all the info.

[1]https://ethresear.ch/t/zero-knowledge-proofs-of-identity-usi...

[c2bo]

Part of the problem is that "normal" digital signatures create correlation factors that can be used to track/profile users, whereas a zero knowledge proof (over knowledge of a valid signature) could prevent this.