| Due to the increased popularity of group-oriented applications and protocols, securing group communication has become a critical networking issue and has received much attention in recent years. A secure and efficient group key management protocol presents one of the most fundamental challenges in group communication security. While key transport protocols may be appropriate for key establishment in one-to-many applications, many collaborative applications require distributed key agreement protocols. Proposals for key agreement protocols that have been published so far do not scale for large size groups. Moreover, the security of most of these protocols has been flawed. This thesis considers the problem of group key agreement protocols from two points of view: efficiency and security. Regarding the efficiency, a novel framework based on the extension of the Diffie-Hellman key exchange protocol is proposed. The efficiency of this framework comes from the distribution of the group members into size-bounded clusters. Using clustering improves the protocol efficiency (in both communication and computation costs), provides fault-tolerance and supports heterogenous systems. A modification to these protocols has been presented to address the problem of key agreement within ad hoc wireless networks. Regarding protocol security, a new approach for key agreement protocols analysis is proposed. To demonstrate the approach, a formal analysis of one of the existing key agreement protocols has been presented where some practical attacks have been identified. It has been shown that the possibility of most of these attacks is due to the use of improper techniques to supply key authentication. Different solutions to address these attacks have been proposed. These solutions provide authenticity and are implemented within the steps required by the key agreement protocol. These authenticated protocols are based on an entanglement of both the ephemeral key and the long-term key to provide authenticated key agreement protocols. |
