Paper 2023/1816

ASOZ: a decentralized payment system with privacy preserving and auditing on public blockchain

Abstract

Decentralized payment systems have gradually received more attention in recent years. By removing the trusted intermediary used for accounting ledgers, those payment systems fundamentally empower users to control their assets. As privacy concerns grow, some cryptocurrencies are proposed to preserve the privacy of users. However, those cryptocurrencies also inadvertently facilitate illicit activities such as money laundering, fraudulent trading, etc. So it is necessary to design an auditing scheme. To solve this problem, many privacy-preserving and auditing schemes have been proposed. However, there exists no scheme that effectively solves the issue of privacy-preserving and auditing on both user identity and transaction value. In this paper, we propose a design for a decentralized payment system named ASOZ. We use cryptographic accumulators based on Merkle trees for accounting and use a combination of Twisted ElGamal, Non-Interactive Zero-Knowledge(NIZK), Bulletproofs, and zk-SNARKs for privacy-preserving and auditing. Our scheme achieves full transaction audit in global mixing, while the additional cost introduced remains within an acceptable range, specifically an 8% increment in proof generation time and a 23% rise in verification time. Our scheme is capable of handling large-scale transaction scenarios such as designated contract markets, and offers the strongest privacy protection capabilities in coin mixer schemes.