Epass: Efficient and Privacy-Preserving Asynchronous Payment on Blockchain

2025-06-11

AI Summary

To address privacy leakage—caused by on-chain transparency exposing users’ financial status—and scalability degradation—resulting from latency-induced transaction overhead—in blockchain-based Buy Now Pay Later (BNPL) asynchronous payments, this paper proposes the first red-chain transaction rectification mechanism integrating locally verifiable signatures with time-lock encryption. The mechanism enables secure, controlled updates to deferred payment states without requiring new on-chain transactions, thereby supporting privacy-preserving asynchronous payments on-chain. Built upon an editable blockchain architecture, it employs formal security modeling and proofs to ensure robustness. Communication overhead is reduced to the kilobyte level, and end-to-end latency is improved by over 4× compared to baseline approaches. Experimental evaluation on a Go-Ethereum private testnet validates both efficiency and practicality.

Technology Category

• Multiagent Systems: Mechanism Design
• Machine Learning: Privacy
• Natural Language Processing: Ethics — Bias, Fairness, Transparency & Privacy

Application Category

• Security and Privacy: Blockchains and distributed ledgers
• Responsible Web: Data and user privacy-enhancing technologies for the Web
• Economics, Online Markets and Human Computation: Economic aspects of blockchain and cryptocurrencies

Abstract

Buy Now Pay Later (BNPL) is a rapidly proliferating e-commerce model, offering consumers to get the product immediately and defer payments. Meanwhile, emerging blockchain technologies endow BNPL platforms with digital currency transactions, allowing BNPL platforms to integrate with digital wallets. However, the transparency of transactions causes critical privacy concerns because malicious participants may derive consumers' financial statuses from on-chain asynchronous payments. Furthermore, the newly created transactions for deferred payments introduce additional time overheads, which weaken the scalability of BNPL services. To address these issues, we propose an efficient and privacy-preserving blockchain-based asynchronous payment scheme (Epass), which has promising scalability while protecting the privacy of on-chain consumer transactions. Specifically, Epass leverages locally verifiable signatures to guarantee the privacy of consumer transactions against malicious acts. Then, a privacy-preserving asynchronous payment scheme can be further constructed by leveraging time-release encryption to control trapdoors of redactable blockchain, reducing time overheads by modifying transactions for deferred payment. We give formal definitions and security models, generic structures, and formal proofs for Epass. Extensive comparisons and experimental analysis show that extsf{Epass} achieves KB-level communication costs, and reduces time overhead by more than four times in comparisons with locally verifiable signatures and Go-Ethereum private test networks.

Problem

• Protects consumer transaction privacy on blockchain
• Reduces time overhead in deferred payments
• Enhances scalability of BNPL services

Innovation

• Locally verifiable signatures for transaction privacy
• Time-release encryption for deferred payments
• Redactable blockchain to reduce time overheads