Baras CSHCN Ph . D . 99 - 2 ( ISR Ph . D . 99 - 4 )

Title of Dissertation: KEY MANAGEMENT FOR SECURE MULTICAST COMMUNICATIONS Raadhakrishnan Poovendran, Doctor of Philosophy, 1999 Dissertation directed by: Professor John S. Baras Department of Electrical and Computer Engineering Providing key management schemes for large scale multicast groups has become an important problem due to many potential commercial applications such as stock quote and software distribution on the Internet. For secure multicast communication, all the group members have to share a common session key. Since the member dynamics such as join or deletion do not necessarily terminate the multicast session, it is important to update the session key to all the valid members, so that the non-members do not have access to the future keys. Finding efficient ways for key generation and distribution in the presence of member dynamics is an actively researched problem. This dissertation considers the single sender, multiple receiver model of secure multicast communication. The goal is to develop schemes that have reduced computational overhead at the time of key generation, minimize the amount of message units required at the time of key updates, and minimize the number of keys to be stored by the sender as well as receivers. In order to achieve this goal, a key generation and distribution architecture based on rooted trees and control panels is proposed. A control panel is assumed to consist of mutually suspicious members who jointly generate the keys that are distributed to the rest of the members. Based on the assumption about the control panel, we provide a distributed key generation mechanism which allows a set of mutually suspicious members to contribute to the generation of a joint secret without revealing their individual contributions. The key distribution scheme presented considers the member revocation event and relates it to the key assignment of individual users. We define and show that the entropy of the member revocation event plays an important role in determining the number of keys assigned to a member. We claim that the number of keys allocated to a member based on the elementary concepts from information theory will also correspond to the minimum number of keys that need to be assigned to a member unless additional functional relationship among keys exists, since it completely captures the uncertainty of the member revocation event. We also identify some weaknesses in the recent schemes in [17, 15], and solve an open problem posed at Eurocrypt’99 [16]. KEY MANAGEMENT FOR SECURE MULTICAST COMMUNICATIONS by Raadhakrishnan Poovendran Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Doctor of Philosophy 1999 Advisory Committee: Professor John S. Baras, Chairman Professor Carlos Berenstein Professor Anthony Ephremides Professor Virgil D. Gligor Professor Lawrance Washington c ©Copyright by Raadhakrishnan Poovendran 1999