A Privacy-Preserving Enforced Bill Collection System Using Smart Contracts

The paper presents a privacy- preserving enforced bill collection system that ensures both user anonymity and accountability using smart contracts and accountable ring signatures. The system extends the existing Isshiki system, which allows users to anonymously access services, by introducing an enforcement mechanism that guarantees payment via pre-deposited funds. If a user ignores the invoice, the smart contract automatically transfers the deposit to the bill collector, ensuring fair compensation. The proposed system is designed for decentralized blockchain environments, specifically using Ethereum smart contracts to enforce payment while maintaining privacy. The solution is efficient, reducing gas costs by leveraging elliptic curve digital signatures (ECDSA).