Abstract: Blockchain is proposed as a technology integrating various technological innovations such as distributed ledger, cryptography, consensus algorithm and P2P (peer-to-peer) network. It realizes decentralization, traceability and tamper resistance in an open environment with mutual distrust nodes. Blockchain has solved the problems of trust establishment, security management and privacy protection that have been plaguing the traditional centralized service architecture, and has been drawing broad attention from various fields of society. Among them, P2P network realizes the final consistency of distributed ledger through consensus algorithm, and utilizes various protocols to coordinate the services provided by each node. Its functionalities are continuously enriched and improved with each technological iteration of blockchain, thus forming a relatively independent blockchain P2P network, which has become the focus of blockchain research. Firstly, this paper systematically introduces the characteristics and key technologies of P2P network, especially the overlay network, resource query and jitter of P2P network. Secondly, the typical blockchain application scenarios are used to analyze the working mechanism and operation characteristics of blockchain P2P network from the perspective of architecture and protocol implementation. Then, the paper introduces the security risks of blockchain P2P network, and discusses the implementation process and prevention methods of typical attacks. Finally, the summary is given by exploring the security challenges and key technical responses in blockchain networks.

Key words: blockchain, peer-to-peer, network security, network architecture, network protocol

摘要： 区块链作为一种分布式账本、密码学、共识算法、P2P（peer-to-peer）网络等多技术创新融合的技术，在一个节点之间互不信任的开放环境中实现了去中心化、防篡改、可溯源等功能，改变了一直困扰传统中心化服务架构的信任建立、安全管理与隐私保护等难题，引起了社会各领域的广泛关注。其中，P2P网络通过共识算法实现了分布式账本的最终一致性，并利用各种协议协调各节点提供的服务，其应用功能随着区块链技术的每一次迭代不断丰富和完善，从而形成了相对独立的区块链P2P网络，成为区块链研究的重点。较为系统地介绍了P2P网络的特征和关键技术，尤其对影响着区块链的P2P覆盖网络、资源查询和网络抖动等技术进行了深入分析；结合典型区块链应用场景，从体系结构和协议实现入手分析了区块链P2P网络的工作机制和运行特点；介绍了区块链P2P网络存在的安全风险，讨论了典型攻击的实施过程及防范方法。最后，总结探索了区块链网络及其安全面临的挑战和主要技术应对。

关键词: 区块链, 对等网络, 网络安全, 网络体系结构, 网络协议