本项目研究VoIP网络安全通信中"匿名认证"和"隐密传输"两大基础性科学问题。重点探索基于生物Token和低熵口令的认证技术，研究通信实体间匿名认证的新方法。在此基础上，构建隐私增强的密钥协商机制，解决VoIP网络中"匿名认证和密钥协商"关键技术问题。并通过引入分形随机行走理论，建立基于分形随机行走的隐密通信理论模型，模拟VoIP网络隐密通信的时延抖动和丢包特征，设计用于计算VoIP媒体分组隐藏容量的算法，构建自适应隐密通信新机制，实现机密信息在VoIP网络中的安全传输，解决VoIP网络中"通信数据隐密传输"关键技术问题。旨在降低机密信息被攻击的概率，增强VoIP网络的通信安全。 该项目的研究成果对VoIP网络通信中的认证和数据安全传输的实现技术进行创新，解决现有安全机制尚未考虑或尚未解决的匿名认证和隐密传输两大科学难题。为实现VoIP网络高效、安全的通信提供重要的理论依据和实践指导。

This project studies two basic scientific problems of anonymous authentication and covert transmission over Voice over Internet Protocol (VoIP) networks, with a special emphasis on exploring the novel authentication method with anonymity by using Token, biometrics and low-entropy passwords. On the basis of the proposed authentication method, an anonymity enhanced authentication key agreement for SIP sessions is proposed to solve the key technological problem of anonymous authentication and key agreement. The project establishes a fractal random walk theoretical model for simulating the characteristics of delay jitter and packet loss in the process of VoIP communications, and calculating the embedding rates of VoIP media packets. A new self-adaptive steganographic method is then established for VoIP networks, so as to realize the secure transmission of confidential information over VoIP networks, and thus solving another key technological problem of covert communications over VoIP networks, thereby reducing the attack probability of confidential information and enhancing the security of VoIP networks. The proposed work would advance knowledge of authentication and secure transmission over VoIP networks, in an attempt to solve the scientific problems of anonymous authentication and covert communications which have not been considered or solved in existing security protocols. The output of the project would provide a theoretical basis and practical instructions for secure and efficient communications over VoIP networks.