> Would zero knowledge proofs work here?

Yes, but that would then require more infrastructure. For example, Australia does not have a national ID card - or a national proof of age card (each state, however, does implement a Proof of Age card, eg https://www.nsw.gov.au/driving-boating-and-transport/driver-...).

So, what is your zero knowledge based on? Who is the signer?

Under the Identity Verification Services Act 2023 we have IDMatch (https://www.idmatch.gov.au/). This whole setup can simply be extended to have third parties act as an intermediary between the government and the party attempting to get proof of age. Similar to AusPost's DigitaliD (https://www.digitalid.com/personal). But let's not have that company owned by the Government :)

It's pretty cooked that we are asking the social media companies to go ahead and prove to the eSaftey commissioner that they have measures in place to stop kids from getting access to social websites, yet they have to use unreliable measures like selfies to do it. The companies can't win here. This won't be the last you hear of this. https://youtu.be/YTwBStZIawY?t=306