Proof-of-work certificates that can be efficiently computed in the cloud

TL;DR

This paper introduces efficient, problem-specific proof-of-work certificates for cloud computing that significantly reduce the computational overhead for the Prover, enabling practical verifiable outsourcing of computations.

Contribution

It presents novel, Prover-optimal proof-of-work methods for specific problems like linear algebra, improving practicality over generic approaches.

Findings

Prover-optimal certificates reduce computational costs.

Efficient verification algorithms enable practical verifiable outsourcing.

Applicable to computer algebra and linear algebra computations.

Abstract

In an emerging computing paradigm, computational capabilities, from processing power to storage capacities, are offered to users over communication networks as a cloud-based service. There, demanding computations are outsourced in order to limit infrastructure costs. The idea of verifiable computing is to associate a data structure, a proof-of-work certificate, to the result of the outsourced computation. This allows a verification algorithm to prove the validity of the result, faster than by recomputing it. We talk about a Prover (the server performing the computations) and a Verifier. Goldwasser, Kalai and Rothblum gave in 2008 a generic method to verify any parallelizable computation, in almost linear time in the size of the, potentially structured, inputs and the result. However, the extra cost of the computations for the Prover (and therefore the extra cost to the customer), although only almost a constant factor of the overall work, is nonetheless prohibitive in practice. Differently, we will here present problem-specific procedures in computer algebra, e.g. for exact linear algebra computations, that are Prover-optimal, that is that have much less financial overhead.