This work deals with the issue of multicast communication, specifically it focuses on group key management. It discusses group key management protocols as well as existing algorithms and algorithm designs for efficient key management and distribution. Based on the knowledge, two solutions were developed. The application for comparing the efficiency of algorithms was created as well. Both existing and proposed schemes were compared using two scenarios. Based on the resulting graphs, the suitability of individual algorithms was evaluated.

Yes / Recently there is a high demand from the Internet Service Providers to transmit multimedia services over high speed wireless networks. These networks are characterized by high mobility receivers which perform frequent handoffs across homogenous and heterogeneous access networks while maintaining seamless connectivity to the multimedia services. In order to ensure secure delivery of multimedia services to legitimate group members, the conventional cluster based group key management (GKM) schemes for securing group communication over wireless mobile multicast networks have been proposed. However, they lack efficiency in rekeying the group key in the presence of high mobility users which concurrently subscribe to multiple multicast services that co-exist in the same network. This paper proposes an efficient multi-service group key management scheme (SMGKM) suitable for high mobility users which perform frequent handoffs while participating seamlessly in multiple multicast services. The users are expected to drop subscriptions after multiple cluster visits hence inducing huge key management overhead due to rekeying the previously visited cluster keys. The already proposed multi-service SMGKM system with completely decentralised authentication and key management functions is adopted to meet the demands for high mobility environment with the same level of security. Through comparisons with existing GKM schemes and simulations, SMGKM shows resource economy in terms of reduced communication and less storage overheads in a high speed environment with multiple visits.

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Yes / Addressing key management in mobile multicast communication is currently a booming topic due to the convergence of wireless and mobile technologies. With the proliferation of multiple group based services that are possible to co-exist within a single network, mobile subscribers could subscribe to these services concurrently while ubiquitous. However, the existing group key management (GKM) protocols intend to secure group communication for just a single group service. The GKM approaches involve inefficient use of keys and huge rekeying overheads, hence unsuitable for multiple multicast group environments. In this paper, we propose a novel GKM protocol for multiple multicast groups, called slot based multiple group key management (SMGKM) scheme. SMGKM supports the movement of single and multiple members across a homogeneous or heterogeneous wireless network while participating in multiple group services with minimized rekeying transmission overheads. Unlike conventional GKM protocols, SMGKM protocol can mitigate 1-affect-n phenomenon, single point of failure and investment pressure of signaling load caused by rekeying at the core network. Numerical analysis and simulation results of the proposed protocol show significant resource economy in terms of communication bandwidth overhead, storage overheads at the Domain Key Distributor (DKD), mobile receiver and Area Key Distributors while providing intense security.

No / Previous cluster based group key management schemes for wireless mobile multicast communication lack efficiency in rekeying the group key if high mobility users concurrently subscribe to multiple multicast services that co-exist in the same network. This paper proposes an efficient multi-service group key management scheme suitable for high mobility users which perform frequent handoffs while participating seamlessly in multiple multicast services. The users are expected to drop subscriptions after multiple cluster visits hence inducing huge key management overhead due to rekeying the previously visited cluster keys. However we adopt our already proposed SMGKM system with completely decentralised authentication and key management functions to address demands for high mobility environment with same level of security and less overhead. Through comparisons with existing schemes and simulations, SMGKM shows resource economy in terms of rekeying communication overhead in high mobility environment with multi-leaves.

No / Abstract: Mobile multicast is recently becoming a hot research in the convergence of wireless and mobile technologies. With the emergence of various multicast-based services, multiple multicast groups are possible to exist within a single network, and mobile subscribers could subscribe to multiple groups concurrently. However, the existing group key management (GKM) protocols intend to secure group communication for just a single group service. The GKM approaches involve inefficient use of keys and huge rekeying overheads, hence unsuitable for multiple multicast group environments. In this paper, we propose a novel GKM protocol for multiple multicast groups, called slot based multiple group key management (SMGKM) scheme. SMGKM supports the movement of single and multiple members across a homogeneous or heterogeneous wireless network while participating in multiple group services with minimized rekeying transmission overheads. Unlike conventional GKM protocols, SMGKM protocol mitigates 1-affect-n phenomenon, single point of failure and investment pressure of signaling load at the core network. The results of the proposed protocol show resource economy in terms of communication bandwidth and storage overheads.

Large-scale wireless sensor networks (WSNs) are highly vulnerable to attacks because they consist of numerous resource-constrained devices and communicate via wireless links. These vulnerabilities are exacerbated when WSNs have to operate unattended in a hostile environment, such as battlefields. In such an environment, an adversary poses a physical threat to all the sensor nodes. An adversary may capture any node, compromising critical security data including keys used for encryption and authentication. Consequently, it is necessary to provide security services to these networks to ensure their survival. We propose a novel, self-organizing key management scheme for large-scale and long-lived WSNs, called Survivable and Efficient Clustered Keying (SECK). SECK provides administrative services that ensures the survivability of the network. SECK is suitable for managing keys in a hierarchical WSN consisting of low-end sensor nodes clustered around more capable gateway nodes. Using cluster-based administrative keys, SECK provides five efficient security administration mechanisms: 1) clustering and key setup, 2) node addition, 3) key renewal, 4) recovery from multiple node captures, and 5) re-clustering. All of these mechanisms have been shown to localize the impact of attacks and considerably improve the efficiency of maintaining fresh session keys. Using simulation and analysis, we show that SECK is highly robust against node capture and key compromise while incurring low communication and storage overhead. / Master of Science

Most of the Internet applications today require multicasting. For example, software updates, multimedia content distribution, interacting gaming and stock data distribution require multicast services. All of these applications require privacy and authenticity of the participants. Most of the multicasting groups are dynamic and some of them are large in number. Only those users who belong to the multicasting group should receive the information and be able to decrypt it. New users joining the group should receive information immediately but should not understand the information that was released prior to their joining. Similarly, if users leave the group, they should not receive any further information and should not be able to decrypt it. Keys need to be distributed to the users belonging to the current session and hence some kind of key management is required. Existing schemes for secure multicasting are limited to small and static groups. To allow large and dynamic groups to use the services of multicasting, some protocols have been developed: Multicast Trees, Spanning Tree, Centralized Tree-Based Key Management, Flat-key Management and Distributed Key Management. Some of these schemes are better than others with respect to the speed, memory consumption, and amount of communication needed to distribute the keys. All these schemes are limited in performance with respect to the speed, memory consumption, and amount of communication needed in distributing the keys. In this thesis, a number of public and private key algorithms and key management techniques for secure and dynamic multicasting are studied and analyzed. The thesis is focused on the secure lock method developed by Chiou and Chen, using the Chinese Remainder Theorem. The protocol is implemented for a small group of users and its performance is studied. While, the secure lock method works well for a small group of users and the performance is degraded when the group grows in size. A protocol is proposed for a large and dynamic group, based on the idea of the Chinese Remainder Theorem. A performance study is carried out by comparing our proposed protocol with the existing multicasting protocols. The analysis shows that the proposed protocol works well for large and dynamic groups and gives significantly better performance. / Master of Science