Smart Contract With Secret Parameters

By design, smart contracts' data and computations are public to all participants. In this paper, we study how to create smart contracts with parameters that need to stay secret. We propose a way to keep some of the parameters off-chain, while guaranteeing correctness of the computation, using a combination of a commitment scheme and a zero-knowledge proof system. We describe an implementation of our construction, based on ethereum smart contracts and zk-SNARKS. We also provide a small example and a cost analysis of our approach.