Tree-Based Group Key Agreement Protocols In Ad Hoc Networks

As group-oriented and collaborative applications is getting popularity, the needs for the secure and reliable group communications increase. One of its important challenges in the secure and reliable group communications is to design secure and efficient group key management. There are two kinds of group key managements: group key distribution for the centralized management and group key agreement for the distributive management. Group key agreement scheme is more adaptable than group key distribution in DPG in which its membership can be frequently changed. As far as the communication and computational cost concerned, the existing group key management protocols such as STR and TGDH can reduce the cost by using binary trees. In the tree-based mechanism, it is noticed that the computational cost can be reduced by lowering the depth of the tree. In this thesis, we propose twomore efficient tree-based key agreement protocols.This paper presents two new protocols based on existing protocols. One is a secure ternary tree based authenticated group key agreement protocol in dynamic scenario. Ternary trees are introduced into key agreement protocol to reduce more rounds than the ones with binary trees and reduce computation complexity from O (log₂m )to O (log₃m ). In contrast to the traditional key distribution scheme, the contributory key agreement avoids the centralized trust and the requirement of the establishment of pairwise secret channels. The other is introducing n-ary trees obtained by extending ternary trees into key agreement protocol, which reduces more rounds than the ones with ternary trees and reduces computation complexity from O (log₃m )to O (log_nm ).At the same time, the scheme takes into account the dynamic case which contains the join and leave scenario and presents a good solution. It, on one hand, ensures the minimum computation complexity. On the other hand, the solution retains the tree structure. At the last, we give a security analysis based on the random oracle security model.