Research On Group Key Agreement Protocols

It is of great necessity to build secure group communication systems to ensure communication security and reliability with the rapid development of the computer technology, communication and network technology, as well as the sharp increase of distributed, collaborative and interactive application system, such as digital conference, collaborative computing, telemedicine, remote education, video on demand systems, etc. In the process, group key agreement as the foundation for a variety of security mechanisms in group-oriented applications plays a key role in the construction of secure group communication.A Group key agreement protocol is a group key establishment technique in which a shared secret is derived by more parties. However, no party engaged can predefined the group key. The group key can be utilized for cryptographic mecha-nisms, like encryption schemes or message authentication codes. Compared with traditional centralized group key distribution mechanisms, group key agreement protocols do not need the central key server. Hence they overcome the difficulties of single point failure. At the same time, in the dynamic environment, we need to consider the dynamic relationship among group members. Currently, related research has already developed from the initial two-party key agreement protocols into dynamic group key agreement protocols.Focusing on provable security, basic protocols and scalability, the thesis devotes to the research of group key agreement protocols. The main contributions and innovations of the thesis are as follows.(1) We propose a stronger and more perfect security model for group key agreement protocols, including participant model, adversary model and security definitions. Especially, based on the strength of adversary capability, we classify the adversary into passive adversary, active adversary and malicious participant; meanwhile we give the corresponding security definitions. (2) We introduce a formal definition of dynamic group key agreement protocol. According to the different logic structures adopted, group key agreement protocols are divided into three classes. Then we put forward three basic corresponding protocols and discuss how to refresh the group key. The "complier" technology may strengthen the security of the basic protocols. Meanwhile, we propose the general principles for designing secure group key agreement protocols.(3) Firstly, a message authentication scheme is designed as a basic block. Based on the MA scheme and motivated by Joux's protocol, we propose an improved secure tripartite authenticated key agreement protocol which can resist all known active attacks and analyze the security and efficiency of TAK-V protocol.Group key agreement protocols are considered as basic blocks in cryptography to ensure the confidentiality and reliability of group communications, which can allow a set of parties to agree upon a common secret session key over a public network. The research and design of dynamic group key agreement protocols has important theore-tical significance and practical value. Thus, it will have a bright prospect.