Jisoo Kim


There have been numerous studies performed on secure group communication over unsecured channels such as the Internet and ad-hoc network. Most of the results are focused on cryptographic methods to share secret keys within the group. In the real world, however, we cannot establish an application for group communication without considering authentication of each peer (group member) since the adversary could digitally disguise itself and intrude into the key sharing process without valid membership. Therefore, authentication is an inevitable component for any secure communication protocols as well as peer group communication. In the classical design of group key protocols, each peer should be authenticated by a separate and centralized authentication server (e.g. Kerberos). Although many practical protocols present efficient ways for authentication, we are still facing the necessity of optimization between authentication and group key sharing. In that sense, implicit key authentication is an ideal property for group key protocols since, once it is possibly put into practice, we do not need any separate authentication procedure as a requisite. There was an attempt to devise implicit key authentication service in conjunction with group key agreement protocol; Authenticated Group Diffie-Hellman (A-GDH) and its stronger version (SA-GDH). Unfortunately, both were proved to have some weakness from the man-in-the-middle attacks. In this project, practical fixes for A-GDH and SA-GDH using Message Authentication Code (MAC) schemes are proposed and performance evaluation is carried out from implementation and experimentation for each: A-GDH, SA-GDH, A-GDH with MAC, and SA-GDH with MAC. Finally, the policies how and where to deploy authenticated GDH protocols are discussed under various group communication scenarios.

Publication Date


Document Type

Master's Project

Student Type


Department, Program, or Center

Computer Science (GCCIS)


Radziszowski, Stanislaw - Chair

Advisor/Committee Member

Bischof, Hans-Peter

Advisor/Committee Member

Kaminsky, Alan


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