Multicast delivery of data is a powerful mechanism that has strong potential in next generation networks. The increased efficiency over unicast is a definite advantage, but the use of multicast poses many security risks. Effectively adding security measures to a multicast service is an intriguing problem, especially when the service is deployed in a wireless setting. Next generation IEEE 802.16 standard WirelessMAN networks are a perfect example of this problem, and the latest draft specification of the standard includes a secure protocol solution called multicast and broadcast rekeying algorithm (MBRA). In this paper, we expose the security problems of MBRA, including non-scalability and omission of backward and forward secrecy, and propose a new approach, ELAPSE, to address these problems. We analyze the security property of ELAPSE and use Qualnet simulations to show its efficiency

Multicast enables efficient large-scale content distribution and has become more and more popular in network service. Security is a critical issue for multicast because many applications require access control and privacy. This issue is more sensitive to wireless network, which is lack of physical boundaries. IEEE 802.16 is the standard for next generation wireless network, which aims to provide the last mile access for wireless metropolitan area network (WirelessMAN). Multicast is also supported in IEEE 802.16, and a multicast and broadcast rekeying algorithm (MBRA) is proposed as an optional function for secure multicast. However, this algorithm does not provide backward and forward secrecy, and is not scalable to large group. This paper reviews the above two deficiencies of MBRA and proposes a new algorithm to address them. We also propose algorithms for secure multicast in different scenarios of WirelessMAN besides its basic scheme.

Effectively adding security measures to a multicast service is an intriguing problem, especially when the service isdeployed in a wireless setting. Next generation IEEE 802.16standard WirelessMAN networks are a perfect example of this problem, and the latest draft specification of the standard includes a secure protocol solution called Multicast and Broadcast Rekeying Algorithm (MBRA). In this paper, we expose the security problems of MBRA, including non-scalability and omission of backward and forward secrecy, and propose new approaches, ELAPSE and ELAPSE+, to address these problems. In particular, ELAPSE+ makes use of membership and mobility information gathered in the application layer to augment the adaptive group management in the MAC layer. We analyze the security property of ELAPSE and ELAPSE+, and compare their performances with MBRA by simulating group rekeying scenarios.

If $f(x)$ and $g(x)$ are relatively prime polynomials in $\mathbb Z[x]$ satisfying certain conditions arising from a theorem of Capelli and if $n$ is an integer $> N$ for some sufficiently large $N$, then the non-reciprocal part of $f(x) x^{n} + g(x)$