A Blockchain-based Protocol of Trusted Setup Ceremony for Zero-Knowledge Proof

Abstract

Zero-knowledge proof is emerging to enable privacy. Among existing techniques, zk-SNARK (Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge) [1] supports the shortest verification time and the smallest proof size. However, using zk-SNARK requires the execution of trusted setup ceremony in advance. The trusted setup ceremony generates common reference string (CRS) which is shared with prover and verifier. Currently, an external trusted third party is assumed for trusted setup ceremony, which causes significant security vulnerability in zk-SNARK. In this paper, we propose a blockchain-based protocol of trusted setup ceremony without trusted third party. Three different types of protocols are classified in terms of where to store CRS and how to validate CRS through pairing check. We analyze the protocol complexity of CRS pairing check computations and on-chain storage space.