SNARKs to the rescue: proof-of-contact in zero knowledge

TL;DR

This paper introduces a zero-knowledge proof protocol for privacy-preserving COVID-19 contact tracing, enabling individuals to prove infection and contact without revealing identities, enhancing decentralization and scalability.

Contribution

It presents a novel cryptographic protocol for proof-of-contact that supports complex exposure proofs while maintaining privacy and decentralization.

Findings

Cryptographic proofs are publicly verifiable.

Supports proofs of nth-order exposure.

Enhances scalability of contact tracing systems.

Abstract

This paper describes techniques to help with COVID-19 automated contact tracing, and with the restoration efforts. We describe a decentralized protocol for ``proof-of-contact'' in zero knowledge where a person can publish a short cryptographic proof attesting to the fact that they have been infected and that they have come in contact with a set of people without revealing any information about any of the people involved. More importantly, we describe how to compose these proofs to support broader functionality such as proofs of $n$th-order exposure which can further speed up automated contact tracing. The cryptographic proofs are publicly verifiable, and places the burden on the person proving contact and not on third parties or healthcare providers rendering the system more decentralized, and accordingly more scalable.