Verifiable Computation Using Multiple Provers

A. J. Blumberg, J. Thaler, V. Vu, and M. Walfish

Abstract: The increasing ubiquity of the cloud computing paradigm has renewed focus on the classical problem of allowing weak clients to check the results of computation delegated to powerful servers. Recent advances in proof-based verifiable computation have led to several near-practical protocols. Protocols based on interactive proofs (IPs) work with highly restrictive models of computation and are thus efficient only for a limited class of computations. In contrast, protocols based on argument systems apply to a much larger class of computations, but efficiency requires amortization of very expensive setup costs.

This paper initiates the study of the practical efficiency of multiprover interactive proofs (MIPs). We present a new MIP for delegating computation that extends insights from a powerful IP protocol (Goldwasser et al., STOC, 2008). Without reductions or amplification, our protocol uses only two provers (departing from prior work on MIPs), and achieves both the efficiency of interactive proof-based protocols and the generality of argument system-based protocols. Also, this result, together with recently developed machinery, creates a potential avenue toward concretely efficient arguments without setup costs.

We describe Clover, a built system for verifiable computation, based on our protocol. Although Clover does not implement the full theory (it has setup costs), it applies to problems that existing IPs cannot efficiently handle, and achieves performance comparable to, or better than, the best argument systems.