An Auditable Decentralized Anonymous Payment Complying with The Least-Privilege Principle

Nowadays, some decentralized anonymous payment (DAP) systems have emerged to protect transaction privacy. However, these systems may be strictly limited by certain governments due to the difficulty of tracking financial flow, which severely restricts their circulation. Although several auditable DAP (ADAP) systems permit authorities to monitor transactions, the potential for privacy violations instead makes users hesitate to apply them. As a result, it becomes a dilemma. Thus, this paper proposes an ADAP system that follows the least-privilege principle, called LP-ADAP, to strike a balance between auditability and privacy preservation. First, LP-ADAP employs a consensus audit mechanism to prevent transactions from being investigated by a single malicious auditor. In addition, the proposed method adheres to the least-privilege principle, strictly limiting auditors to only the minimum necessary permissions, thus limiting the privacy leakage of the senders and receivers. Finally, auditors in LP-ADAP can conduct offline audits without participating in the transaction phase, reducing their burden. Experiment results show that LP-ADAP outperforms existing mechanisms in transaction generation and verification. Moreover, the transaction size of LP-ADAP is mostly smaller than that of other methods, even when the number of auditors increases. Consequently, LP-ADAP is the most practical and trustworthy DAP system.