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Rabi N Mahapatra - One of the best experts on this subject based on the ideXlab platform.
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key Predistribution schemes for establishing pairwise keys with a mobile sink in sensor networks
IEEE Transactions on Parallel and Distributed Systems, 2011Co-Authors: Amar Rasheed, Rabi N MahapatraAbstract:Security services such as authentication and pairwise key establishment are critical to sensor networks. They enable sensor nodes to communicate securely with each other using cryptographic techniques. In this paper, we propose two key Predistribution schemes that enable a mobile sink to establish a secure data-communication link, on the fly, with any sensor nodes. The proposed schemes are based on the polynomial pool-based key Predistribution scheme, the probabilistic generation key Predistribution scheme, and the Q-composite scheme. The security analysis in this paper indicates that these two proposed Predistribution schemes assure, with high probability and low communication overhead, that any sensor node can establish a pairwise key with the mobile sink. Comparing the two proposed key Predistribution schemes with the Q-composite scheme, the probabilistic key Predistribution scheme, and the polynomial pool-based scheme, our analytical results clearly show that our schemes perform better in terms of network resilience to node capture than existing schemes if used in wireless sensor networks with mobile sinks.
Robert O Bonow - One of the best experts on this subject based on the ideXlab platform.
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concordance and discordance between stress redistribution reinjection and rest redistribution thallium imaging for assessing viable myocardium comparison with metabolic activity by positron emission tomography
Circulation, 1993Co-Authors: Vasken Dilsizian, Nanette Freedman, Stephen L Bacharach, Pasquale Perronefilardi, James A Arrighi, Arshed A Quyyumi, Robert O BonowAbstract:BACKGROUND Stress thallium scintigraphy provides important diagnostic and prognostic information in patients with coronary artery disease by demonstrating regional myocardial ischemia. However, if the clinical question being addressed is whether a region is viable and not whether there is inducible ischemia, then it may be more reasonable to perform rest-redistribution imaging rather than stress-redistribution imaging followed by either reinjection or late redistribution. Therefore, we determined whether stress-redistribution-reinjection and rest-redistribution imaging provide the same information regarding myocardial viability. METHODS AND RESULTS Both stress-redistribution-reinjection and rest-redistribution thallium single photon emission computed tomographic imaging was performed in 41 patients with chronic stable coronary artery disease, with quantitative analysis of regional thallium activity. Thallium reinjection was performed immediately after the 3- to 4-hour redistribution images were completed. Of the 155 myocardial regions with perfusion defects on the stress images, 91 (59%) were irreversible on conventional 3- to 4-hour redistribution images. When the outcomes of these irreversible regions were assessed after reinjection and compared with rest-redistribution images, there was concordance of data regarding myocardial viability (normal/reversible or irreversible) in 72 of the 91 (79%) irreversible defects. Twenty of the 41 patients also underwent positron emission tomography at rest with [18F]fluorodeoxyglucose and [15O]water. In these patients, stress-redistribution-reinjection and rest-redistribution imaging provided concordant information regarding myocardial viability in 427 (72%) of 594 myocardial regions and discordance in 167 regions. However, when irreversible thallium defects were further analyzed according to the severity of the thallium defect in these discordant regions, 149 of 167 (89%) demonstrated only mild-to-moderate reduction in thallium activity (51% to 85% of normal activity), and positron emission tomography verified 98% of these regions to be metabolically active and viable. Thus, when the severity of thallium activity was considered within irreversible thallium defects, the concordance between stress-redistribution-reinjection and rest-redistribution imaging regarding myocardial viability increased to 94%. CONCLUSIONS These data indicate that one of two imaging modalities, either stress-redistribution-reinjection or rest-redistribution imaging, may be used for identifying viable myocardium. However, if there are no contraindications to stress testing, stress-redistribution-reinjection imaging provides a more comprehensive assessment of the extent and severity of coronary artery disease by demonstrating regional myocardial ischemia without jeopardizing information on myocardial viability.
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regional thallium uptake in irreversible defects magnitude of change in thallium activity after reinjection distinguishes viable from nonviable myocardium
Circulation, 1992Co-Authors: Vasken Dilsizian, Nanette Freedman, Stephen L Bacharach, Pasquale Perronefilardi, Robert O BonowAbstract:BACKGROUNDThallium reinjection immediately after stress-redistribution imaging identifies ischemic but viable myocardium in as many as 50% of the regions characterized by conventional redistribution imaging as irreversibly injured. However, we have previously shown that some regions in which irreversible defects persist despite reinjection are metabolically active, and hence viable, by positron emission tomography. In the current study, we determined whether the severity of reduction in thallium activity within irreversible defects on redistribution images and the magnitude of change in regional thallium activity after reinjection can further discriminate viable from nonviable myocardium in such defects.METHODS AND RESULTSWe studied 150 patients with coronary artery disease by exercise thallium tomography using the rest-reinjection protocol. The three sets of images (stress, redistribution, and reinjection) were then analyzed quantitatively. The increase in regional thallium activity from redistribution t...
Peng Ning - One of the best experts on this subject based on the ideXlab platform.
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group based key Predistribution for wireless sensor networks
ACM Transactions on Sensor Networks, 2008Co-Authors: Donggang Liu, Peng NingAbstract:Many key Predistribution techniques have been developed recently to establish pairwise keys between sensor nodes in wireless sensor networks. To further improve these schemes, researchers have also proposed to take advantage of the sensors' expected locations and discovered locations to help the Predistribution of the keying materials. However, in many cases, it is very difficult to deploy sensor nodes at their expected locations or guarantee the correct location discovery at sensor nodes in hostile environments. In this article, a group-based deployment model is developed to improve key Predistribution. In this model, sensor nodes are only required to be deployed in groups. The critical observation in the article is that the sensor nodes in the same group are usually close to each other after deployment. This deployment model is practical; it greatly simplifies the deployment of sensor nodes, while still providing an opportunity to improve key Predistribution. Specifically, the article presents a novel framework for improving key Predistribution using the group-based deployment knowledge. This framework does not require the knowledge of the sensors' expected or discovered locations and is thus suitable for applications where it is difficult to deploy the sensor nodes at their expected locations or correctly estimate the sensors' locations after deployment. To seek practical key Predistribution schemes, the article presents two efficient instantiations of this framework, a hash key-based scheme and a polynomial-based scheme. The evaluation shows that these two schemes are efficient and effective for pairwise key establishment in sensor networks; they can achieve much better performance than the previous key Predistribution schemes when the sensor nodes are deployed in groups.
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Improving key Predistribution with deployment knowledge in static sensor networks
ACM Transactions on Sensor Networks, 2005Co-Authors: Donggang Liu, Peng NingAbstract:Pairwise key establishment is a fundamental security service for sensor networks. However, establishing pairwise keys in sensor networks is a challenging problem, particularly due to the resource constraints on sensor nodes and the threat of node compromises. This article proposes to use both predeployment and postdeployment knowledge to improve pairwise key Predistribution in static sensor networks. By exploiting the predeployment knowledge, this article first develops two key Predistribution schemes, a closest pairwise keys scheme and a closest polynomials scheme. The analysis shows that these schemes can achieve better performance if the expected location information is available and that the smaller the deployment error is, the better performance they can achieve. The article then investigates how to use postdeployment knowledge to improve pairwise key Predistribution in static sensor networks. The idea is to load an excessive amount of predistributed keys on sensor nodes, prioritize these keys based on sensors' actual locations discovered after deployment, and discard low-priority keys to thwart node compromise attacks. This approach is then used to improve the random subset assignment scheme proposed recently to demonstrate its practicality and effectiveness. The analysis indicates that the postdeployment knowledge can also greatly improve the performance and security of key Predistribution.
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establishing pairwise keys in distributed sensor networks
Computer and Communications Security, 2003Co-Authors: Donggang Liu, Peng NingAbstract:Pairwise key establishment is a fundamental security service in sensor networks; it enables sensor nodes to communicate securely with each other using cryptographic techniques. However, due to the resource constraints on sensors, it is infeasible to use traditional key management techniques such as public key cryptography and key distribution center (KDC). To facilitate the study of novel pairwise key Predistribution techniques, this paper presents a general framework for establishing pairwise keys between sensors on the basis of a polynomial-based key Predistribution protocol [2]. This paper then presents two efficient instantiations of the general framework: a random subset assignment key Predistribution scheme and a grid-based key Predistribution scheme. The analysis in this paper indicates that these two schemes have a number of nice properties, including high probability (or guarantee) to establish pairwise keys, tolerance of node captures, and low communication overhead. Finally, this paper presents a technique to reduce the computation at sensors required by these schemes.
Adelino V Lopes - One of the best experts on this subject based on the ideXlab platform.
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neutral axis depth and moment redistribution in frp and steel reinforced concrete continuous beams
Composites Part B-engineering, 2015Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Abstract The neutral axis depth is considered the best parameter for quantifying the moment redistribution in continuous concrete beams, as exemplified in various design codes worldwide. It is therefore important to well understand the variation of neutral axis depth against moment redistribution. This paper describes a theoretical investigation into the neutral axis depth and moment redistribution in concrete beams reinforced with fibre reinforced polymer (FRP) and steel bars. A finite element model has been developed. The model predictions are in favourable agreement with experimental results. Three types of reinforcement are considered, namely, glass fibre, carbon fibre and steel. Various levels of reinforcement ratio are used for a parametric evaluation. The results indicate that FRP reinforced concrete continuous beams exhibit significantly different response characteristics regarding the moment redistribution and variation of neutral axis depth from those of steel reinforced ones. In addition, it is found that the code recommendations are generally unsafe for calculating the permissible moment redistribution in FRP reinforced concrete beams, but the neglect of redistribution in such beams may be overconservative.
Keith M Martin - One of the best experts on this subject based on the ideXlab platform.
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Graph-theoretic design and analysis of key Predistribution schemes
Designs Codes and Cryptography, 2016Co-Authors: Michelle Kendall, Keith M MartinAbstract:Key Predistribution schemes for resource-constrained networks are methods for allocating symmetric keys to devices in such a way as to provide an efficient trade-off between key storage, connectivity and resilience. While there have been many suggested constructions for key Predistribution schemes, a general understanding of the design principles on which to base such constructions is somewhat lacking. Indeed even the tools from which to develop such an understanding are currently limited, which results in many relatively ad hoc proposals in the research literature. It has been suggested that a large edge-expansion coefficient in the key graph is desirable for efficient key Predistribution schemes. However, attempts to create key Predistribution schemes from known expander graph constructions have only provided an extreme in the trade-off between connectivity and resilience: namely, they provide perfect resilience at the expense of substantially lower connectivity than can be achieved with the same key storage. Our contribution is twofold. First, we prove that many existing key Predistribution schemes produce key graphs with good expansion. This provides further support and justification for their use, and confirms the validity of expansion as a sound design principle. Second, we propose the use of incidence graphs and concurrence graphs as tools to represent, design and analyse key Predistribution schemes. We show that these tools can lead to helpful insights and new constructions.
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ABroadcast-enhanced Key Predistribution Schemes
2015Co-Authors: Michelle Kendall, Keith M Martin, Maura Paterson B. DouglasAbstract:Schemes (BEKPSs). These schemes are suitable for networks with access to a trusted base station and an authenticated broadcast channel. We demonstrate that the access to these extra resources allows for the creation of BEKPSs with advantages over key Predistribution schemes such as flexibility and more efficient revocation. There are many possible ways to implement BEKPSs, and we propose a framework for describing and analysing them. In their paper ‘From key Predistribution to key redistribution’, Cichoń, Go lȩbiewski and Kuty lowski propose a scheme for ‘redistributing ’ keys to a wireless sensor network using a broadcast channel after an initial key Predistribution. We classify this as a BEKPS and analyse it in that context. We provide simpler proofs of some results from their paper, give a precise analysis of the resilience of their scheme, and discuss possible modifications. We then study two scenarios where BEKPSs may be particularly desirable and propose a suitable family of BEKPSs for each case. We demonstrate that they are practical and efficient to implement, and our analysis shows their effectiveness in achieving suitable trade-offs between the conflicting priorities in resource-constrained networks. 1
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broadcast enhanced key Predistribution schemes
ACM Transactions on Sensor Networks, 2014Co-Authors: Michelle Kendall, Keith M Martin, Maura B Paterson, Douglas R StinsonAbstract:We present a formalisation of a category of schemes that we refer to as broadcast-enhanced key Predistribution schemes (BEKPSs). These schemes are suitable for networks with access to a trusted base station and an authenticated broadcast channel. We demonstrate that the access to these extra resources allows for the creation of BEKPSs with advantages over key Predistribution schemes such as flexibility and more efficient revocation. There are many possible ways to implement BEKPSs, and we propose a framework for describing and analysing them.In their paper “From Key Predistribution to Key Redistribution,” Cichon et al. [2010] propose a scheme for “redistributing” keys to a wireless sensor network using a broadcast channel after an initial key Predistribution. We classify this as a BEKPS and analyse it in that context. We provide simpler proofs of some results from their paper, give a precise analysis of the resilience of their scheme, and discuss possible modifications. We then study two scenarios where BEKPSs may be particularly desirable and propose a suitable family of BEKPSs for each case. We demonstrate that they are practical and efficient to implement, and our analysis shows their effectiveness in achieving suitable trade-offs between the conflicting priorities in resource-constrained networks.
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broadcast enhanced key Predistribution schemes
IACR Cryptology ePrint Archive, 2012Co-Authors: Michelle Kendall, Keith M Martin, Maura B Paterson, Douglas R StinsonAbstract:We present a formalisation of a category of schemes which we call Broadcast-enhanced Key Predistribution Schemes (BEKPSs). These schemes are suitable for networks with access to a trusted base station and an authenticated broadcast channel. We demonstrate that the access to these extra resources allows for the creation of BEKPSs with advantages over key Predistribution schemes such as flexibility and more efficient revocation. There are many possible ways to implement BEKPSs, and we propose a framework for describing and analysing them. In their paper ‘From key Predistribution to key redistribution’, Cichon, Go lȩbiewski and Kuty lowski propose a scheme for ‘redistributing’ keys to a wireless sensor network using a broadcast channel after an initial key Predistribution. We classify this as a BEKPS and analyse it in that context. We provide simpler proofs of some results from their paper, give a precise analysis of the resilience of their scheme, and discuss possible modifications. We then study two scenarios where BEKPSs may be particularly desirable and propose a suitable family of BEKPSs for each case. We demonstrate that they are practical and efficient to implement, and our analysis shows their effectiveness in achieving suitable trade-offs between the conflicting priorities in resource-constrained networks.
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on the role of expander graphs in key Predistribution schemes for wireless sensor networks
IACR Cryptology ePrint Archive, 2011Co-Authors: Michelle Kendall, Keith M MartinAbstract:Providing security for a wireless sensor network composed of small sensor nodes with limited battery power and memory can be a nontrivial task. A variety of key Predistribution schemes have been proposed which allocate symmetric keys to the sensor nodes before deployment. In this paper we examine the role of expander graphs in key Predistribution schemes for wireless sensor networks. Roughly speaking, a graph has good expansion if every ‘small’ subset of vertices has a ‘large’ neighbourhood, and intuitively, expansion is a desirable property for graphs of networks. It has been claimed that good expansion in the product graph is necessary for ‘optimal’ networks. We demonstrate flaws in this claim, argue instead that good expansion is desirable in the intersection graph, and discuss how this can be achieved. We then consider key Predistribution schemes based on expander graph constructions and compare them to other schemes in the literature. Finally, we propose the use of expansion and other graph-theoretical techniques as metrics for assessing key Predistribution schemes and their resulting wireless sensor networks.