The rapid development of the AI agent communication protocols, including the Model Context Protocol (MCP), Agent2Agent (A2A), Agora, and Agent Network Protocol (ANP), is reshaping how AI agents communicate with tools, services, and each other. While these protocols support scalable multi-agent interaction and cross-organizational interoperability, their security principles remain understudied, and standardized threat modeling is limited; no protocol-centric risk assessment framework has been established yet. This paper presents a systematic security analysis of four emerging AI agent communication protocols. First, we develop a structured threat modeling analysis that examines protocol architectures, trust assumptions, interaction patterns, and lifecycle behaviors to identify protocol-specific and cross-protocol risk surfaces. Second, we introduce a qualitative risk assessment framework that identifies twelve protocol-level risks and evaluates security posture across the creation, operation, and update phases through systematic assessment of likelihood, impact, and overall protocol risk, with implications for secure deployment and future standardization. Third, we provide a measurement-driven case study on MCP that formalizes the risk of missing mandatory validation/attestation for executable components as a falsifiable security claim by quantifying wrong-provider tool execution under multi-server composition across representative resolver policies. Collectively, our results highlight key design-induced risk surfaces and provide actionable guidance for secure deployment and future standardization of agent communication ecosystems.

翻译：包括模型上下文协议（MCP）、代理间协议（A2A）、Agora以及代理网络协议（ANP）在内的AI代理通信协议正在快速发展，重塑着AI代理与工具、服务及彼此之间的交互方式。尽管这些协议支持可扩展的多代理交互与跨组织互操作性，但其安全原则尚未得到充分研究，标准化的威胁建模仍显不足；目前尚未建立以协议为中心的风险评估框架。本文对四种新兴AI代理通信协议进行了系统性安全分析。首先，我们开发了一种结构化的威胁建模分析方法，通过审视协议架构、信任假设、交互模式及生命周期行为，识别出协议特定及跨协议的风险暴露面。其次，我们引入了一个定性风险评估框架，该框架识别出十二种协议级风险，并通过系统评估可能性、影响及总体协议风险，评估了创建、运行和更新各阶段的安全态势，为安全部署和未来标准化提供了参考。最后，我们针对MCP提供了一个基于测量的案例研究，通过量化代表性解析策略下多服务器组合中错误提供者工具执行的情况，将可执行组件缺失强制性验证/证明的风险形式化为可证伪的安全主张。综合而言，我们的研究结果揭示了关键的设计诱发风险暴露面，并为代理通信生态系统的安全部署和未来标准化提供了可操作的指导。