Every modern passport and ID card has a digital signature and private key in it. 121 counties and counting. This signature is signed by the issuing government and can be used to prove you have a real valid passport. The passport chip even contains a photo signed by the government. The zk passport team are working on doing on device face detection and proving a liveness check against the person holding the phone. 🤯 And yes all of this can be proven inside s clients side zero knowledge proof. Welcome to the age of privacy preserving identity checks.