ZK-Disclosure: Privacy-Preserving Information Disclosure for Digital Evidence with C2PA and zk-SNARKs

Abstract

This paper presents a framework that integrates the Coalition for Content Provenance and Authenticity (C2PA) standard with Zero-Knowledge Proofs (ZKPs), specifically the Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge (zk-SNARKs), to enable verifiable yet privacy-preserving authentication of digital images. Using the ZoKrates toolkit, the system derives a non-revealing fingerprint from the image, generates a succinct proof of integrity, and embeds this proof into C2PA-compliant metadata without exposing the underlying content. The proof can be verified locally or on the Ethereum blockchain using a Groth16 smart contract verifier, providing decentralized and auditably transparent validation. This capability allows journalists, victims, and legal professionals to attest to the existence and integrity of sensitive evidence while deferring its disclosure. Experimental results show that proof verification is highly efficient, requiring approximately 0.01 s, and that the entire workflow is reproducible within containerized environments. The proposed integration of zk-SNARKs with C2PA establishes a practical foundation for secure digital provenance, privacy-preserving evidence management, and strengthened trust in digital media ecosystems.