Refereed Delegation of Computation Using Smart Contracts

Outsourcing computation enables a weak client to expand its computational power as the need arises. A basic requirement of outsourcing computation is the guarantee that the computation result is correct. Cryptographic solutions that provide verifiability for the computation result when the computation is outsourced to a single server, are complex and fragile. We consider the intuitive approach of verifiable computation, called verifiable computation by replication, when the computation is replicated on multiple servers, and a referee decides the result of the final computation using the outputs of all servers. We consider the case when a smart contact is used as the referee. We propose a security model in the Universal Composability (UC) framework of Canetti, and design a 2-server and an n-server protocol with proved security in our model. Our protocols build on the Refereed Delegation of Computation (RDoC) framework of Canetti, Riva, and Rothblum, underline the challenges of using a smart contract as a referee, and address those challenges in the designed protocols. We give the efficiency analysis of the protocols, provide a proof of concept implementation for our protocols using Ethereum smart contact, and give concrete cost values for an example computation.