With this zkApp, users can prove that they are older than 18 on the blockchain on a zero-knowledge basis using hash chains. The idea is to prove you are old enough to do some actions on the web without revealing any more information about yourself.

An example would be to purchase liquor online provided you are older than the legal drinking age (here assumed 18). The zkApp is at a very early stage. Currently, it only provides a similar interface to the sudoku example. To make it a fun project despite the absence of a trusted authority to sign the user’s encrypted (and genuine) information, there is an additional, optional facial verification / identification pipeline built into the app.

It matches the faces on a passport image and a selfie image, assesses the validity of the passport image, and encrypts the user’s age it obtained from the passport. It can therefore replace a trusted third party in a way.

Github: https://github.com/btemuer/pageApp