Epass: Efficient and Privacy-Preserving Asynchronous Payment on Blockchain

TL;DR

Epass introduces an efficient blockchain-based asynchronous payment scheme that enhances privacy and scalability for BNPL services by using locally verifiable signatures and time-release encryption.

Contribution

The paper presents a novel privacy-preserving asynchronous payment scheme (Epass) that reduces time overheads and enhances privacy in blockchain-based BNPL platforms.

Findings

Achieves KB-level communication costs.

Reduces time overhead by over four times.

Provides formal security proofs and extensive experimental validation.

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 \textsf{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.