Thanks for the read, I learned something today! I worry, though, that even if someone could devise a ZPK for age verification, can end-users actually trust that platforms are using it? Say for example Meta provides a biometric-based ZPK for age. Can we trust that they're not harvesting our biometric data? In the podcast's examples, it's easy for Peggy and Victor to understand that they are using a ZPK system. However, the age verification problem most often arises in arrangements where the prover is using a client app into whose inner workings they have no insight (either because it's closed source, they're not technologically literate enough, or who has the time to scrutinize the source code for every program they use) and which is most likely developed by the verifier. So the problem kind of moves upstream: how can you trust that ZPK is actually being used?