Research On Key Agreement Protocols In Ad Hoc Networks

Key establishment is one of the research topics of key management. As the security of secret key constitute the foundation of all secure cryptosystems, it is necessary to establish the session keys before any secure protocols are implemented. One common sense goes that the efficiency of symmetric cryptosystem is superior to that of asymmetric cryptosystem, so it is good for sharing a symmetric key among all the parties in the group. A preferred and effective method of establishing symmetric session keys in dynamic peer group is key agreement protocol. A secure and Communication-Efficient Key Agreement protocol (CEKA) is proposed on the basis of the analysis of Ad hoc networks. The CEKA protocol employs the generalized Diffie-Hellman protocol for two parties and the Joux's protocol for three parties as basic key agreement protocols and extends them to multiparties in Ad hoc networks. In addition, the hierarchical routing protocol in Ad hoc networks has also been used, which can divide the network into different clusters in terms of the degree of vicinity. In this way, it is possible to place the neighboring nodes in clusters as neighbors in the logical key agreement structure. As a result, the 1-hop assumption that most classical group key agreement protocols assume implicitly is weakened, therefore our protocol would be more applicable in Ad hoc networks. In order to withstanding common active attacks, an identity based signature scheme is also proposed, which is existentially unforgeable under a non-adaptively chosen message attack in Random Oracle model. When apply the signature scheme to CEKA protocol, which would be authenticated. Furthermore, the communicational and computational complexity of CEKA protocol has also been analyzed carefully in this thesis. The comparison among the three protocols of CEKA, TGDH and ESTR indicates that CEKA is the most efficient protocol when considering the delay of transmission. Therefore, the proposed scheme is applicable to ad hoc networks with large size and strong dynamicity. Furthermore, the analysis of security shows that our protocol possesses the secure attributes of key independence, perfect forward secrecy, no key-compromise impersonation and no key control. Lastly, an emulation system of CEKA protocol and many cryptographic primitives are realized in software. The experiment results prove that the analysis is true and our protocol is feasible and efficient in practice.