【作者】 陈娟；

【导师】 梁伟；

【作者基本信息】 湖南大学 ， 计算机科学与技术， 2023， 硕士

【摘要】 众包作为一种创新型的经济模式,它充分利用了人类的智慧去解决计算机无法处理的复杂问题,近年来在社会上引起了极大的关注。然而,大多数现有的众包系统,都依赖于第三方中心服务器来处理众包任务的相关交易流程,这些服务器容易受到传统基于信任模型的缺陷影响。随着众包用户数据的快速增长,用户隐私和任务数据有可能被泄露,单点故障和不公平评判的现象有可能发生。随着对公平和隐私问题的逐渐重视,许多学术研究都在寻求通过区块链技术来避免中心化机制带来的缺陷。为了解决现有众包中存在的信任、隐私以及过于中心化的问题,本文研究分析了现有的区块链技术和链下通道技术,并结合加密算法提出了一个新的去中心化的众包机制:(1)针对区块链系统中交易吞吐量低和延迟高的问题,本文基于账户模型和UTXO模型,分别设计了一种高效的链下支付协议来支持众包任务中的支付交易,并进行了模块测试实验,表明该链下支付通道的建立是可行、安全和高效的。(2)结合区块链技术,构建分布式的众包交易模型,在不需要可靠的第三方中心机构的支持下便能够实现通用的发包和接包流程,解决了中心式众包平台中信任建立和高额服务费用的问题。(3)结合密码学算法,对基于区块链众包机制中的数据进行加密保护。采用CPABE加密算法并对其进行改进,将其应用到细粒度的工人访问控制阶段,对加密的任务数据进行访问权限的设置。(4)基于IPFS技术,设计了一种链上链下协同存储方案。通过将众包的原始数据转存到链下节点,相应的哈希值存储到链上,从而缓解了链上节点的存储压力并提高了区块链的吞吐量和可扩展性。(5)对所提众包方案的完备性和安全性进行形式化分析,并对易遭受的攻击进行抵抗性评估。实验表明,本文所提出的链上链下协同存储的区块链众包机制是有效、实用和可行的。更多还原

【Abstract】 Crowdsourcing,as an innovative economic model that makes full use of human intelligence to solve complex problems that cannot be handled by computers,has attracted great attention in recent years.Most existing crowdsourcing systems,however,rely on third-party central servers to handle the transaction processes associated with crowdsourcing tasks,and these servers are vulnerable to the shortcomings of traditional trust-based models.With the rapid growth of crowdsourcing users’ data,users’ privacy and tasks’ data are potentially compromised,and single points of failure and unfair judging are likely to occur.With the growing focus on fairness and privacy issues,many academic studies are seeking to avoid the flaws caused by centralized mechanisms through blockchain technology.In order to solve the problems of trust,privacy and over-centralization in existing crowdsourcing,this paper researches and analyzes the existing blockchain technology as well as off-chain channel technology,and proposes a new decentralized crowdsourcing mechanism combined with cryptographic algorithms:(1)To address the problems of low transaction throughput and high latency in blockchain systems,this paper designs an efficient off-chain payment protocol to support payment transactions in crowdsourcing tasks based on the account model and the UTXO model,respectively.And modular testing experiments are conducted to show that the establishment of off-chain payment channel is feasible,secure and efficient.(2)Combining with blockchain technology to build a distributed crowdsourcing transaction model,it can realize a common process of issuing and receiving contracts without the support of a reliable third-party central institution,solving the problems of trust building and high service costs in centralized crowdsourcing platforms.(3)Combining cryptographic algorithms to encrypt and protect the data in the blockchain-based crowdsourcing mechanism.The CPABE encryption algorithm is adopted and improved to apply it to the fine-grained worker access control stage to set access rights to the encrypted task data.(4)Based on IPFS technology,an on-chain and off-chain collaborative storage scheme is designed.By dumping the original data of crowdsourcing to the off-chain nodes and storing the corresponding hash values to the blockchain,it relieves the storage pressure of the on-chain nodes and improves the throughput and scalability of the blockchain.(5)The completeness and security of the proposed crowdsourcing scheme are analyzed formally,and the vulnerability to attacks is evaluated.Experiments show that the proposed blockchain crowdsourcing mechanism for on-chain and off-chain collaborative storage is effective,practical and feasible.更多还原