【作者】 田甜；

【导师】 王琦；

【作者基本信息】 北京邮电大学 ， 电子与通信工程， 2018， 硕士

【摘要】 随着数据价值的不断攀升,以及数据规模的不断壮大,运用数据共享机制来挖取数据背后的潜在价值也变得越来越重要。在当今的社会大环境下,如何让数据信息拥有者相互之间放下猜忌,彼此信任,避免存在非法获取数据或攻击的情况,这是数据共享的基本需求和共识。传统的数据共享依靠中心化的数据共享方案虽然能够解决系统中互相不信任的问题,但是数据都集中于第三方机构之上,一旦受到攻击就存在数据被删除或修改的风险。区块链技术运用非对称加密算法(哈希算法和数字签名算法)等基础技术使得其具有去信任和去中心化的特点,能改变目前传统的中心化机制,系统节点相互平等存在,集体维护一个可靠数据库,有效解决恶意攻击问题,数据的删除或修改变得几乎不可能,增加了数据可信度和安全性。鉴于此,本论文提出一种基于非对称加密算法的可信数据共享系统。采用非对称加密技术处理用户共享数据,哈希算法提取文件数据,由数字签名算法对其签名并验证,P2P对等网络用于传输和接收加密数据,最后采用块链式记录文件记录用户上传文件的基本信息。非对称加密技术和记录文件的不可篡改性,提高了本系统的可信度和数据安全性。主要的研究工作和成果如下所示:1、系统分为用户注册登录模块、数据上传下载模块和记录文件管理模块。对此3大模块又详细划分为8个子模块。对每个模块提出需求分析和详细设计,其中记录文件管理模块实现记录文件更新操作,记录全网数据,同时全网记录文件会定时交流并检测,并为用户提供历史记录查询操作;数据上传模块和验证模块中使用了非对称加密中的哈希算法(MD5)和数字签名算法(MD5withRSA),以及P2P网络技术(多播通讯模式)。记录文件更新和检测模块使用了 Merkle Tree技术和链接特性。2、采用JavaWeb编程技术,在Eclipse集成环境中开发并测试,能够顺利实现系统开发并进行数据共享。子模块的主要测试结果如下:(1)在数据上传模块中,MD5算法能成功生成每个文件的MD5值,系统生成私钥并由MD5withRSA数字签名算法对其签名,多播模式对象将签名数据传输至网络中。(2)数据验证模块能成功接收到网络中的数据并验证处理。(3)记录文件更新会按照设定的内容格式记录全网上传信息,并且每个时间整点会自动生成新的记录文件。(4)记录文件检测模块中,系统每隔5分钟检测用户记录文件是否保持全网一致,如果存在修改的情况,立马进行数据修复,保证记录文件的统一性。3、模块间联合测试。测试操作一致性。不同用户在成功登录后可同时实现文件的上传共享,且均能一致地按照成功上传时间记录所有上传文件的基本信息到最新的记录文件中,同时用户也能对历史上传记录进行查询以及对文件下载;测试记录文件的一致性和防篡改性。不同用户得到的所有记录文件信息完全保持一致,完整记录着当前时间之前所有的成功上传记录。记录文件如果被恶意删除或修改,定时检测功能会在下一次检测时将数据恢复,用户再次获取的记录文件还是未曾修改的完整文件。测试表明:全历史的记录文件确保数据的完整性,防篡改特性加强了共享数据的安全保护,该系统为用户提供了一个安全可信的数据共享平台。更多还原

【Abstract】 With the increasing value and the growing scale of data,it is becoming more and more important to use data sharing mechanism to extract potential value behind data.In today’s social environment,how to allow data owners to get rid of suspicion,trust each other to avoid illegal access or attack to data,which are the basic requirements and consensus of data sharing.The problem of distrust can be solved in traditional data sharing system which relies on centralized sharing scheme,but data are concentrated on the third party mechanism.Once attacked,there is a risk that the data may be deleted or modified.Blockchain uses basic techniques such as asymmetric cryptography(hash algorithm and digital signature algorithm)to make it have the characteristics of de-trust and decentralization,which can change the traditional centralization mechanism.The nodes in the blockchain system exist equally.Maintaining a reliable database collectively can solve the problem of malicious attack effectively.Data deletion or modification becomes almost impossible,which increases the credibility and security of data.In view of this,a trusted data sharing system based on asymmetric encryption algorithm is put forward in this paper.Asymmetric encryption technology is used to process user-shared data.The hash algorithm is used to extract the file data digest.The digest is signed and verified by digital signature algorithm.The P2P network is used to transmit and receive encrypted data.Finally,record-files are used to record the basic information of users’ uploading files.Asymmetric encryption technology and the indiscriminate modification of record-files improves the credibility and data security of the system.The main research work and results are showed as follows:1.The system is divided into user register and login module,data upload and download module,and record-files management module.The three major modules are further divided into eight sub-modules.The requirements analysis and detail design of each module are given.The record-files management module updates record-files,and records the whole network data at the same time,the whole network record-files can be regularly exchanged and tested.This module also provides historical records query operation for the users;Hash algorithm(MD5)and digital signature algorithm(MD5withRSA)in the asymmetric encryption and P2P network(multicast communication mode)are used in data upload module and verification module.Link characteristics and Merkle Tree technology are used in record-files update and detection modules.2.The system is implemented by JavaWeb programming technology,further developed and tested in the Eclipse integrated environment,it can realize the system development and share the data smoothly.The main test results of sub modules are as follows:(1)In the data upload module,the MD5 algorithm can successfully calculate the MD5 value of each file,the system generates a private key and signs file message by the MD5withRSA digital signature algorithm,and the multicast mode object transfers the signature data to the network.(2)The data validation module can successfully receive the data in the network and verify the processing.(3)The record-files update can record the whole network success upload information according to the set content format,and the new block file can be automatically generated at every hour.(4)In record-files detection module,the system detects whether the local record-files are the same as the whole network data every 5 minutes.If there is any modification,the data is repaired immediately,so as to ensure the consistency of the record-files3.Joint test between modules.Test the operation consistency.After successful login,different users can simultaneously upload and share files,and they also can consistently record the basic information of all uploaded files to the latest record-file according to the successful upload time.At the same time,users can also query the history of uploading records and download files.Test the consistency and tampering of the record-files.All record-files obtained by different users are completely consistent,and all successful upload records before the current time are completely recorded.If a record-file is maliciously deleted or modified,the timing detection module will restore the data,the next obtained record-files are still complete files that have not been modified.The test shows that:the full history of the record file can ensure the integrity of the data,Anti-tamper characteristics strengthen the security of shared data protection.The system provides users with a secure and trusted data sharing platform.更多还原