P2P网络中信用机制的研究与实现-智能与分布计算实验室

P2P网络中信用机制的研究与实现

姓名	何云天
论文答辩日期	2007.05.31
论文提交日期	2007.06.17
论文级别	硕士
中文题名	P2P网络中信用机制的研究与实现
英文题名	Research and Realization of Credit Mechanism in P2P Network
导师1	卢正鼎
导师2
中文关键词	对等网络;信用点模型;信用机制;自动审计
英文关键词	Peer-to-Peer Network;Credit Model;Credit Mechanism;Automatic Audit
中文文摘	P2P（Peer-to-Peer）技术具有分布式的特性并且能够充分利用资源，这使得基于其上的应用得到了快速的发展。但是，由于P2P网络缺乏集中控制，free-riding现象，即“搭顺风车”现象，成为P2P网络，特别是P2P文件共享网络的一个突出的问题，从而成为了制约P2P文件共享系统发展的一个重要因素。目前，人们已经提出了一些试图解决P2P文件共享系统free-riding问题的方案。但是有的方案不够理想，无法应对恶意节点的作弊行为；有的方案代价比较昂贵，需要过多的人为干预，或是需要服务器的管理。所以，针对这些方案的弱点设计了一种信用点模型来刻画节点的贡献和消费。随后在此信用点模型的基础上设计了反映节点历史行为的各种维护信息，包括：信用点信息、交易记录信息和兴趣节点列表信息。同时，设计了节点之间进行维护信息同步的几种策略，来确保P2P文件共享系统中的节点对其兴趣节点有深刻的了解。以上述模型和策略为基础，提出了一种针对节点维护信息数据完整性的自动审计机制。自动审计机制是以一定概率发起的针对三种维护信息的审计，其目的是让P2P文件共享网络中的节点能够自动地探测其兴趣节点是否存在恶意行为（诸如：夸大信用点、协同作弊、诋毁清白节点等行为），通过不断发起的审计达到逐渐找出恶意节点并将其排除在P2P文件共享网络之外的效果，从而使P2P文件共享系统获得健康的、持久的生命力。在P2P文件共享系统中实现了这套信用机制，给出了机制的具体模块实现以及各模块的工作流程。然后对此机制进行了仿真实验和性能分析，验证其在P2P文件共享应用系统中的有效性。
英文文摘	Because of its distributed characteristic and making resources being more fully utilized, P2P (Peer-to-Peer) technology can be used to improve many applications. But in current P2P network, free-riding phenomenon has become a serious problem, especially in P2P file-sharing network, because of lacking centralized control. It finally comes to be an important fact of restricting development of P2P file-sharing systems. So far, A number of solutions have been proposed to address the free-riding problem in peer-to-peer file sharing systems. The solutions are either imperfect?they allow some users to cheat the system with malicious behavior, or expensive?they require human intervention, or require servers. Terefore, we design a credit model to describe the contribution and consumption of peers in order to avoid those weaknesses. Subsequently, on the basis of this credit model, we design various of maintenance information to record peers’ histories, which includes: credit information, trade records information, and interested peer list infomation. Meanwhile, we design several strategies for synchronizing peers’ maintenance information, to ensure that peer in P2P file-sharing system has sound knowledge of its interested peers. Then, we put forward an automatic audit mechanism on the basis of above-mentioned model and strategies. The automatic audit mechanism is initiated for auditing three kinds of maintenance information by certain probability, and it’s purpose is to allow any peer in P2P file-sharing system can automatically detect malicious behavior of its interested peers(such as: exaggerated credit, conspiracy, blame transfer). Peer continuously initiated the audit to gradually identify malicious peers and exclude them from P2P file-sharing system, so that P2P file-sharing system will be healty and has lasting vitality. We realize this credit mechanism in a P2P file-sharing system, and simulate it to analyse its performance and validity.