Secure and reliable group communication is an increasingly active research area by growing popularity in group-oriented and collaborative application. One of the important challenges is to design secure and efficient group key management. While centralized management is often appropriate for key distribution in large multicast-style groups, many collaborative group settings require distributed key agreement. The communication and computation cost is one of important factors in the group key

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... gement for Dynamic Peer Group. In this paper, we extend TGDH (Tree-based Group Diffie-Hellman) protocol to improve the computational efficiency by utilizing pairing-based cryptography. The resulting protocol reduces computational cost of TGDH protocol without degrading the communication complexity. This should be contrasted with the obvious extension of the conventional Diffie-Hellman key distribution protocol to three parties requiring two interactions per peer entity. We extend this three-party key agreement protocol to group key agreement protocol using ternary tree and also use two-party key agreement protocol for some subtree node. Y. Kim et al.[9] proposed a secure, simple and efficient key management method, called TGDH(Tree-based Group Diffie-Hellman) protocol, which uses key tree with Diffie-Hellman key exchange to efficiently compute and update group keys. Since the computation cost of tree-based key management is proportional to the height of configured key tree. Using ternary key tree, we can reduce the computation cost O(log 2 n) of TGDH to O(log 3 n). This paper is organized as follows: Section 2 briefly introduces previous work in group key management, group membership events and bilinear map. Section 3 explains the protocol. Performance analysis is described in Section 4. We suggest concluding remarks in Section 5 following with the security analysis of our protocol in Appendix.