A Zero-Knowledge Version of vSQL

Zero-knowledge arguments of knowledge are powerful cryptographic primitives that allow a computationally strong prover to convince a weaker verifier for the validity of an NP statement, without revealing anything about the corresponding witness (beyond its existence). Most state-of-the art implementations of such arguments that achieve succinct communication and verification cost follow the quadratic arithmetic program paradigm. One notable exception to this is the vSQL system of [Zhang et al. IEEE S&P 2017] which takes an entirely different approach resulting is significantly fewer cryptographic operations. However, it has the notable downside that is not zero-knowledge (i.e., it does not hide the witness from the verifier), a property that has proven to be of utmost importance in many application (e.g., in cryptocurrencies). In this work, we present a zero-knowledge version of the argument upon which vSQL is based. Our construction utilizes two separate techniques: (i) a novel zero-knowledge verifiable polynomial delegation protocol, and (ii) running parts of the argument of vSQL over homomorphic commitments, thus hiding the committed values.