A new group key agreement scheme based on ternary tree

Abstract

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. While group key distribution is often appropriate in large multicast-style groups, not a few collaborative group environments require group key agreement scheme. Group key agreement scheme is more adaptable than group key distribution in communication environments such as DPG (Dynamic Peer Group) in which its membership can be frequently changed and the communicating party in a group can be dynamically configured. In this thesis, we focus on the key agreement protocol in DPG environment with low communication and computational cost. As far as the communication and computational cost concerned, the existing group key management protocols such as STR (Steer) and TGDH (Tree-based Group Key Agreement) reduce the cost O(n) to O($log_2n$) by using binary tree. 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 more efficient key agreement protocols, i.e., skinny tree-based group key agreement and ternary tree-based group key agreement, by applying the pairing-based cryptography to STR and TGDH respectively. Through our proposed protocols, we substitute the binary key tree with the ternary tree and lower the depth of key tree, thus we reduce the computational cost required in protocols. Unlike most of the existing group key agreement protocols which focus on reducing the computational cost, STR is optimized in communication cost at the expense of the computational cost O(n). However, our skinny tree-based group key agreement reduces the...