[论文解读] B-Ride: Ride Sharing with Privacy-preservation, Trust and Fair Payment atop Public Blockchain

Mohamed Baza, Noureddine Lasla+3 more|arXiv (Cornell University)|Jun 21, 2019

Blockchain Technology Applications and Security被引用 7

一句话总结

B-Ride 提出了一种基于公共区块链的去中心化拼车系统，通过时间锁定存款、零知识集合成员证明以及按里程付费机制，确保隐私、信任与公平支付。该系统有效防范了Sybil攻击与免费搭车行为，同时支持基于声誉的司机选择，并已在以太坊测试网上成功部署，证明了其可行性。

ABSTRACT

Ride-sharing is a service that enables drivers to share their trips with other riders, contributing to appealing benefits of shared travel costs. However, the majority of existing platforms rely on a central third party, which make them subject to a single point of failure and privacy disclosure issues. Moreover, they are vulnerable to DDoS and Sybil attacks due to malicious users involvement. Besides, high fees should be paid to the service provider. In this paper, we propose a decentralized ride-sharing service based on public Blockchain, named B-Ride. Both riders and drivers can find rides match while preserving their trip data, including pick-up/drop-off location, and departure/arrival date. However, under the anonymity of the public blockchain, a malicious user may submit multiple ride requests or offers, while not committing to any of them, to discover better offer or to make the system unreliable. B-Ride solves this problem by introducing a time-locked deposit protocol for a ride-sharing by leveraging smart contract and zero-knowledge set membership proof. In a nutshell, both a driver and a rider have to show their commitment by sending a deposit to the blockchain. Later, a driver has to prove to the blockchain on the agreed departure time that he has arrived at the pick-up location. To preserve rider/driver location privacy by hiding the exact pick-up location, the proof is done using zero-knowledge set membership protocol. Moreover, to ensure a fair payment, a pay-as-you-drive methodology is introduced based on the elapsed distance of the driver and the rider. Also, we introduce a reputation-based trust model to rate drivers based on their past trips to allow riders to select them based on their history on the system. Finally, we implement B-Ride in a test net of Ethereum. The experiment results show the applicability of our protocol atop the existing real-world blockchain.

研究动机与目标

• 消除拼车服务对中心化第三方的依赖，避免单点故障与数据泄露风险。
• 在实现拼车匹配的同时，隐藏乘客与司机的确切上下车位置，保护其隐私。
• 通过时间锁定存款与可验证的距离报告，防止免费搭车与虚假索赔，确保信任与公平性。
• 在无中心化监管的情况下，实现基于声誉的司机选择机制，维护系统的长期完整性。
• 实施按里程付费模式，确保根据实际行驶距离实现公平补偿。

提出的方法

• 利用公共区块链（以太坊）与智能合约，在无需信任的环境中管理拼车请求、匹配、存款与支付。
• 采用时间锁定存款协议，要求乘客与司机在拼车匹配前将资金存入智能合约。
• 使用零知识集合成员（ZKSM）证明，验证拼车资格的同时不暴露确切的上车或下车位置。
• 通过链上存储的声誉模型，基于历史行为对司机进行评分，实现透明且去中心化的信任管理。
• 通过距离验证机制强制实现公平支付，司机的报酬基于实际行驶距离，且该数据在链上可验证。
• 通过要求经济承诺与到达时间的密码学证明，防范Sybil攻击。

实验结果

研究问题

• RQ1 如何在保护用户隐私的同时，利用公共区块链实现拼车服务的去中心化并确保信任？
• RQ2 如何防止恶意用户在无承诺的情况下提交多个拼车请求，从而滥用匿名性？
• RQ3 在无第三方依赖的无信任环境中，如何强制实现公平支付？
• RQ4 如何在保障安全与可验证拼车匹配的同时，保护乘客与司机的身份信息？
• RQ5 是否可以在链上实现声誉系统，以在无中心化监管的情况下激励诚实行为？

主要发现

• B-Ride协议通过时间锁定存款与密码学承诺证明，成功防范了Sybil攻击与免费搭车行为。
• 零知识集合成员证明实现了隐私保护的拼车匹配，无需暴露确切的上车或下车位置。
• 按里程付费机制确保了基于实际行驶距离的公平补偿，且通过链上验证得以保障。
• 声誉系统实现了基于历史行为的去中心化、透明的司机选择，提升了系统的可信度。
• 该系统已在以太坊测试网上成功部署与测试，证明了其链上与链下性能的实际可行性。