Using combined keying materials for key distribution in wireless sensor networks

In this paper, we propose a probabilistic key predistribution scheme for wireless sensor networks that increases connectivity of the basic scheme while keeping sizes of keyring and key pool fixed. We introduce the concept of XORed key, which is the bitwise XOR of two regular (a.k.a. single) keys. Sensor nodes are preloaded with a mixture of single and XORed keys. Nodes establish secure links by using shared XORed keys whenever possible. If node pairs do not have any shared XORed or single keys, they transfer keys from their secure neighbors in a couple of ways, and use them to match with their XORed keys. In this way, the probability of securing links, i.e. local connectivity, increases. The decision of which key is to be transferred from which node is given based on local information at the hand of the nodes. We aim to control the resilience of the network against node capture attacks by using XORed keys since an attacker has to know either both single key operands or the XORed key itself. Simulations show that our scheme is up to 50% more connected as compared to basic scheme. Also it has better resilience performance at the beginning of a node capture attack. When it starts to deteriorate, the difference between the resilience of our proposed scheme and basic scheme is not greater than 5%

From carbon nanotubes and silicate layers to graphene platelets for polymer nanocomposites

In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy–graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical conductivity and thermal mechanical behaviour. Graphene platelets (GnPs) of 3.5

Cross-layer design of multi-hop wireless networks

MULTI -hop wireless networks are usually defined as a collection of nodes equipped with radio transmitters, which not only have the capability to communicate each other in a multi-hop fashion, but also to route each others’ data packets. The distributed nature of such networks makes them suitable for a variety of applications where there are no assumed reliable central entities, or controllers, and may significantly improve the scalability issues of conventional single-hop wireless networks. This Ph.D. dissertation mainly investigates two aspects of the research issues related to the efficient multi-hop wireless networks design, namely: (a) network protocols and (b) network management, both in cross-layer design paradigms to ensure the notion of service quality, such as quality of service (QoS) in wireless mesh networks (WMNs) for backhaul applications and quality of information (QoI) in wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of this Ph.D. dissertation, different network settings are used as illustrative examples, however the proposed algorithms, methodologies, protocols, and models are not restricted in the considered networks, but rather have wide applicability. First, this dissertation proposes a cross-layer design framework integrating a distributed proportional-fair scheduler and a QoS routing algorithm, while using WMNs as an illustrative example. The proposed approach has significant performance gain compared with other network protocols. Second, this dissertation proposes a generic admission control methodology for any packet network, wired and wireless, by modeling the network as a black box, and using a generic mathematical 0. Abstract 3 function and Taylor expansion to capture the admission impact. Third, this dissertation further enhances the previous designs by proposing a negotiation process, to bridge the applications’ service quality demands and the resource management, while using WSNs as an illustrative example. This approach allows the negotiation among different service classes and WSN resource allocations to reach the optimal operational status. Finally, the guarantees of the service quality are extended to the environment of multiple, disconnected, mobile subnetworks, where the question of how to maintain communications using dynamically controlled, unmanned data ferries is investigated