A Privacy-Preserving Zero-Knowledge Proof for Blockchain

Zero-Knowledge Proof (ZKP) is a useful tools for proving that a prover possesses a secret without revealing it to the verifier. Designated Verifier Proof (DVP) is a special type of ZKP that adds the ability to restrict the identity of verifiers so that only pre-determined authorized verifiers can verify. However, DVP and other similar schemes do not work if the verifier provides some additional information to indicate the provenance of the proof. Since this information may be stored on the blockchain, the proof can be accepted by third parties even if the verifier is willing to protect the privacy of the prover. In this paper, we propose the concept of Blockchain Designated Verifier Proof (BDVP), and design a BDVP scheme suitable for blockchain applications. The key technique behind our BDVP scheme is that the verifier can forge a fake secret to simulate the proof. Therefore, a third party cannot determine whether the prover possesses the secret. This enables the verifier to protect the privacy of the prover, which is required by law or regulation. We also address the quantum attack problem and propose a post-quantum solution. We evaluate and compare the performances of the proposed protocol with other related protocols.