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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Credit-Based User Authentication for Delay Tolerant Mobile Wireless Networks

Almotairi, Khaled Hatem January 2007 (has links)
Wireless Internet has become increasingly popular due to anywhere anytime access feature. The Internet architecture was designed underlying the existing of the end-to-end path connection. The promise of wireless Internet networks is to provide roaming users connectivity anywhere anytime. However, quality of service (QoS) is still an open issue in wireless networks, which are characterized by possible intermittent connectivity and large transmission delays, due to user mobility, sparse mobile node distribution, link failures (because of hostile propagation medium), and/or other high-priority traffc. In this thesis, a credit-based user authentication scheme is proposed for delay tolerant mobile wireless networks. The proposed authentication scheme isolates the uncertain network condition in the high delay wireless backhaul with high error rate, and accelerates the overall authentication process when the mobile terminal roams in the visited network. Furthermore, an analytical study of overall network performance is presented for the authentication scheme in terms of authentication cost and delay. Simulation results demonstrate that the proposed credit-based authentication scheme reduces the overall real time transaction cost and delay for delay tolerant mobile wireless networks.
2

Security in Delay Tolerant Networks

Zhu, Haojin 27 April 2009 (has links)
Delay- and Disruption-tolerant wireless networks (DTN), or opportunistic networks, represent a class of networks where continuous end-to-end connectivity may not be possible. DTN is a well recognized area in networking research and has attracted extensive attentions from both network designers and application developers. Applications of this emergent communication paradigm are wide ranging and include sensor networks using scheduled intermittent connectivity, vehicular DTNs for dissemination of location-dependent information (e.g., local ads, traffic reports, parking information, etc.), pocket-switched networks to allow humans to communicate without network infrastructure, and underwater acoustic networks with moderate delays and frequent interruptions due to environmental factors, etc. Security is one of the main barriers to wide-scale deployment of DTNs, but has gained little attention so far. On the one hand, similar to traditional mobile ad hoc networks, the open channel and multi-hop transmission have made DTNs vulnerable to various security threats, such as message modification/injection attack or unauthorized access and utilization of DTN resources. On the other hand, the unique security characteristics of DTNs including: long round-trip delay, frequent disconnectivity, fragmentation, opportunistic routing as well as limited computational and storage capability, make the existing security protocols designed for the conventional ad hoc networks unsuitable for DTNs. Therefore, a series of new security protocols are highly desired to meet stringent security and efficiency requirements for securing DTNs. In this research, we focus on three fundamental security issues in DTNs: efficient DTN message (or bundle) authentication, which is a critical security service for DTN security; incentive issue, which targets at stimulating selfish nodes to forward data for others; and certificate revocation issue, which is an important part of public key management and serves the foundation of any DTN security protocols. We have made the following contributions: First of all, the unique ``store-carry-and-forward'' transmission characteristic of DTNs implies that bundles from distinct/common senders may opportunistically be buffered at some common intermediate nodes. Such a ``buffering'' characteristic distinguishes DTN from any other traditional wireless networks, for which intermediate cache is not supported. To exploit such buffering opportunities, we propose an Opportunistic Batch Bundle Authentication Scheme (OBBA) to dramatically reduce the bundle authentication cost by seamlessly integrating identity-based batch signatures and Merkle tree techniques. Secondly, we propose a secure multi-layer credit based incentive scheme to stimulate bundle forwarding cooperation among DTNs nodes. The proposed scheme can be implemented in a fully distributed manner to thwart various attacks without relying on any tamper-proof hardware. In addition, we introduce several efficiency-optimization techniques to improve the overall efficiency by exploiting the unique characteristics of DTNs. Lastly, we propose a storage-efficient public key certificate validation method. Our proposed scheme exploits the opportunistic propagation to transmit Certificate Revocation List (CRL) list while taking advantage of bloom filter technique to reduce the required buffer size. We also discuss how to take advantage of cooperative checking to minimize false positive rate and storage consumption. For each research issue, detailed simulation results in terms of computational time, transmission overhead and power consumption, are given to validate the efficiency and effectiveness of the proposed security solutions.
3

Credit-Based User Authentication for Delay Tolerant Mobile Wireless Networks

Almotairi, Khaled Hatem January 2007 (has links)
Wireless Internet has become increasingly popular due to anywhere anytime access feature. The Internet architecture was designed underlying the existing of the end-to-end path connection. The promise of wireless Internet networks is to provide roaming users connectivity anywhere anytime. However, quality of service (QoS) is still an open issue in wireless networks, which are characterized by possible intermittent connectivity and large transmission delays, due to user mobility, sparse mobile node distribution, link failures (because of hostile propagation medium), and/or other high-priority traffc. In this thesis, a credit-based user authentication scheme is proposed for delay tolerant mobile wireless networks. The proposed authentication scheme isolates the uncertain network condition in the high delay wireless backhaul with high error rate, and accelerates the overall authentication process when the mobile terminal roams in the visited network. Furthermore, an analytical study of overall network performance is presented for the authentication scheme in terms of authentication cost and delay. Simulation results demonstrate that the proposed credit-based authentication scheme reduces the overall real time transaction cost and delay for delay tolerant mobile wireless networks.
4

Security in Delay Tolerant Networks

Zhu, Haojin 27 April 2009 (has links)
Delay- and Disruption-tolerant wireless networks (DTN), or opportunistic networks, represent a class of networks where continuous end-to-end connectivity may not be possible. DTN is a well recognized area in networking research and has attracted extensive attentions from both network designers and application developers. Applications of this emergent communication paradigm are wide ranging and include sensor networks using scheduled intermittent connectivity, vehicular DTNs for dissemination of location-dependent information (e.g., local ads, traffic reports, parking information, etc.), pocket-switched networks to allow humans to communicate without network infrastructure, and underwater acoustic networks with moderate delays and frequent interruptions due to environmental factors, etc. Security is one of the main barriers to wide-scale deployment of DTNs, but has gained little attention so far. On the one hand, similar to traditional mobile ad hoc networks, the open channel and multi-hop transmission have made DTNs vulnerable to various security threats, such as message modification/injection attack or unauthorized access and utilization of DTN resources. On the other hand, the unique security characteristics of DTNs including: long round-trip delay, frequent disconnectivity, fragmentation, opportunistic routing as well as limited computational and storage capability, make the existing security protocols designed for the conventional ad hoc networks unsuitable for DTNs. Therefore, a series of new security protocols are highly desired to meet stringent security and efficiency requirements for securing DTNs. In this research, we focus on three fundamental security issues in DTNs: efficient DTN message (or bundle) authentication, which is a critical security service for DTN security; incentive issue, which targets at stimulating selfish nodes to forward data for others; and certificate revocation issue, which is an important part of public key management and serves the foundation of any DTN security protocols. We have made the following contributions: First of all, the unique ``store-carry-and-forward'' transmission characteristic of DTNs implies that bundles from distinct/common senders may opportunistically be buffered at some common intermediate nodes. Such a ``buffering'' characteristic distinguishes DTN from any other traditional wireless networks, for which intermediate cache is not supported. To exploit such buffering opportunities, we propose an Opportunistic Batch Bundle Authentication Scheme (OBBA) to dramatically reduce the bundle authentication cost by seamlessly integrating identity-based batch signatures and Merkle tree techniques. Secondly, we propose a secure multi-layer credit based incentive scheme to stimulate bundle forwarding cooperation among DTNs nodes. The proposed scheme can be implemented in a fully distributed manner to thwart various attacks without relying on any tamper-proof hardware. In addition, we introduce several efficiency-optimization techniques to improve the overall efficiency by exploiting the unique characteristics of DTNs. Lastly, we propose a storage-efficient public key certificate validation method. Our proposed scheme exploits the opportunistic propagation to transmit Certificate Revocation List (CRL) list while taking advantage of bloom filter technique to reduce the required buffer size. We also discuss how to take advantage of cooperative checking to minimize false positive rate and storage consumption. For each research issue, detailed simulation results in terms of computational time, transmission overhead and power consumption, are given to validate the efficiency and effectiveness of the proposed security solutions.
5

Reliable Communications over Heterogeneous Wireless Networks

Samuel, Hany January 2011 (has links)
The recent years have seen an enormous advance in wireless communication technology and co-existence of various types of wireless networks, which requires effective inter-networking among the heterogeneous wireless networks in order to support user roaming over the networks while maintaining the connectivity. One of main challenges to achieve the connectivity over heterogeneous wireless networks is potential intermittent connections caused by user roaming. The issue is how to maintain the connection as the user roams and how to ensure service quality in the presence of a long disconnection period. In this dissertation, we apply the delay tolerant network (DTN) framework to heterogeneous terrestrial wireless networks, and propose a system architecture to achieve the connectivity in the presence of excessive long delays and intermittent paths. We study several possible approaches, discuss the applicability of each of the approaches and propose the super node architecture. To demonstrate the effectiveness of the proposed super node architecture, we give a simulation study that compares the system performance under the super node architecture and under the epidemic based architecture. Within the proposed architecture that employs the idea of super nodes, we further study how to effectively route a message over access networks. We present a new routing technique for mobile ad-hoc networks (MANETs) based on the DTN system architecture. We introduce the concept of virtual network topology and redefine the dominating-set based routing for the challenged network environment under consideration. In addition, we propose a time based methodology to predict the probability of future contacts between node pairs to construct the virtual network topology. We present a simulation study that demonstrates the effectiveness of the proposed routing approach as compared with the epidemic routing, and that the time based technique for predicting the future contacts gives better performance compared with that using the number of previous contacts. We further extend the dominating set routing technique through analyzing the underlying node mobility model. We shed some light on how using node mobility model can improve contact probability estimation. Based on our findings we propose a new algorithm that improves the routing performance by minimizing the selected dominating set size. Information security challenges in the super node architecture are introduced. We further address two main security challenges: The first is how to prevent unauthorized nodes from using the network resources, and the second is how to achieve end-to-end secure message exchange over the network. Our proposed solutions are based on asymmetric key cryptography techniques. Moreover, we introduce a new idea of separating the problem of source authentication from the problem of message authorization. We propose a new technique that employs the one-way key chain to use symmetric key cryptographic techniques to address the problems under consideration.
6

Message Forwarding and Scheduling in Delay Tolerant Networks

Elwhishi, Ahmed January 2012 (has links)
Delay-tolerant networking (DTN) has recently received considerable attention from the research community. This type of networks is characterized by frequent disconnections due to propagation phenomena, node mobility, and power outages. Thus, the complete path between the source and the destination may never have existed. This context requires the design of new communication paradigms and techniques that will make communication possible in these environments. To achieve message delivery, researchers have proposed the use of store-carry-and-forward protocols, whereby a node may store the message and carry it until an appropriate forwarding opportunity arises. Many flooding-routing schemes have been proposed for DTNs in order to increase the probability of message delivery. However, these schemes suffer from excessive energy consumption, severe contention that significantly degrades their performance, especially if we account for the fact that each node could be a hand-held and battery-powered device with stringent buffer size limitation. With such buffer limitations at the DTN nodes, message drop/loss could happen due to buffer overflow. In order to address the problem and improve the performance of DTNs, this thesis focuses on two main design objectives; first, the design and evaluation of new multi-copy routing schemes; second, the design and evaluation of new scheduling and dropping policies to reduce message drop/loss due to buffer overflow. To fulfill the first objective, a protocol called Self Adaptive Routing Protocol (SARP) is introduced. It is a multi-copy scheme designed to suit resource-sufficient DTNs. Based on SARP, two multi-copy routing schemes are further developed to suit resource-limited DTNs, in which compensating the traffic demand become a challenge: i) the Self Adaptive Utility-based Routing Protocol (SAURP), ii) and the Adaptive Reinforcement based Routing Protocol (ARBRP). The introduced protocols form a new framework of DTNs aiming to significantly reduce the resource requirements of flooding-based routing schemes. Each introduced scheme has its own way of exploring the possibility of taking mobile nodes as message carriers in order to increase the delivery ratio of the messages. In SAURP, the best carrier for a message characterized by jointly considering the inter-contact time that is obtained using a novel contact model and the network status, such as including wireless link condition and nodal buffer availability. In ARBRP, the routing problem is solved by manipulating a collaborative reinforcement learning technique, where a group of nodes can cooperate with each other to make a forwarding decision for the stored messages based on a cost function at each contact with another node. ARBRP is characterized by not only considering the contact time statistics, but also looks into the feedback on user behavior and network conditions, such as congestion and buffer occupancy sampled during each previous contact with any other node. The thesis argues and proves that the nodal movement and the predicted collocation with the message recipient can serve as meaningful information to achieve an intelligent message forwarding decision at each node. Therefore, the introduced protocols can achieve high efficiency via an adaptive and intelligent routing mechanism according to network conditions. To fulfill the second objective, we further enhanced the performance of DTN routing by introducing message scheduling and dropping policies such that the delivery ratio is increased and/or the delivery delay is reduced. This thesis investigates new buffer management and scheduling policies to improve the performance of flooding and utility-based forwarding routing in DTNs, such that the forwarding/dropping decision can be made at a node during each contact for either optimal message delivery ratio or message delivery delay. To examine their effectiveness, the introduced protocols and the buffer management and scheduling policies have been implemented and compared to a number of existing counterpart approaches. A near-realistic mobility model is used for testing. A number of scenarios are used to evaluate the performance of the introduced techniques in terms of delivery delay, ratio, and the number of transmissions performed.
7

Opportunistic routing in intermittently connected wireless mobile social networks

Khosravi, Arian 07 May 2012 (has links)
Consumer electronics such as cellular phones and portable computers with short-range communication capabilities have enabled the large-scale information dissemination through user mobility and contact, without the assistance of communication infrastructures. In such a new communication paradigm, one challenge is to determine when and how to forward a message to the destination, possibly through a series of third parties. This problem has attracted a lot of attention in the literature lately, with proposals ranging from epidemic to single or multi-copy spray and wait or focus strategies. However most existing work assumed independent or identically distributed mobility. Observing most human mobility and interaction are interest-driven in the real world, in this research, we evaluate the performance of these schemes with an interest-driven mobility model. We further propose to take the user interest into account when determining routing strategies to further improve the performance of these schemes for mobile social networks. Simulation results have demonstrated the efficacy of the interest-aware routing strategies. / Graduate
8

Reliable Communications over Heterogeneous Wireless Networks

Samuel, Hany January 2011 (has links)
The recent years have seen an enormous advance in wireless communication technology and co-existence of various types of wireless networks, which requires effective inter-networking among the heterogeneous wireless networks in order to support user roaming over the networks while maintaining the connectivity. One of main challenges to achieve the connectivity over heterogeneous wireless networks is potential intermittent connections caused by user roaming. The issue is how to maintain the connection as the user roams and how to ensure service quality in the presence of a long disconnection period. In this dissertation, we apply the delay tolerant network (DTN) framework to heterogeneous terrestrial wireless networks, and propose a system architecture to achieve the connectivity in the presence of excessive long delays and intermittent paths. We study several possible approaches, discuss the applicability of each of the approaches and propose the super node architecture. To demonstrate the effectiveness of the proposed super node architecture, we give a simulation study that compares the system performance under the super node architecture and under the epidemic based architecture. Within the proposed architecture that employs the idea of super nodes, we further study how to effectively route a message over access networks. We present a new routing technique for mobile ad-hoc networks (MANETs) based on the DTN system architecture. We introduce the concept of virtual network topology and redefine the dominating-set based routing for the challenged network environment under consideration. In addition, we propose a time based methodology to predict the probability of future contacts between node pairs to construct the virtual network topology. We present a simulation study that demonstrates the effectiveness of the proposed routing approach as compared with the epidemic routing, and that the time based technique for predicting the future contacts gives better performance compared with that using the number of previous contacts. We further extend the dominating set routing technique through analyzing the underlying node mobility model. We shed some light on how using node mobility model can improve contact probability estimation. Based on our findings we propose a new algorithm that improves the routing performance by minimizing the selected dominating set size. Information security challenges in the super node architecture are introduced. We further address two main security challenges: The first is how to prevent unauthorized nodes from using the network resources, and the second is how to achieve end-to-end secure message exchange over the network. Our proposed solutions are based on asymmetric key cryptography techniques. Moreover, we introduce a new idea of separating the problem of source authentication from the problem of message authorization. We propose a new technique that employs the one-way key chain to use symmetric key cryptographic techniques to address the problems under consideration.
9

Message Forwarding and Scheduling in Delay Tolerant Networks

Elwhishi, Ahmed January 2012 (has links)
Delay-tolerant networking (DTN) has recently received considerable attention from the research community. This type of networks is characterized by frequent disconnections due to propagation phenomena, node mobility, and power outages. Thus, the complete path between the source and the destination may never have existed. This context requires the design of new communication paradigms and techniques that will make communication possible in these environments. To achieve message delivery, researchers have proposed the use of store-carry-and-forward protocols, whereby a node may store the message and carry it until an appropriate forwarding opportunity arises. Many flooding-routing schemes have been proposed for DTNs in order to increase the probability of message delivery. However, these schemes suffer from excessive energy consumption, severe contention that significantly degrades their performance, especially if we account for the fact that each node could be a hand-held and battery-powered device with stringent buffer size limitation. With such buffer limitations at the DTN nodes, message drop/loss could happen due to buffer overflow. In order to address the problem and improve the performance of DTNs, this thesis focuses on two main design objectives; first, the design and evaluation of new multi-copy routing schemes; second, the design and evaluation of new scheduling and dropping policies to reduce message drop/loss due to buffer overflow. To fulfill the first objective, a protocol called Self Adaptive Routing Protocol (SARP) is introduced. It is a multi-copy scheme designed to suit resource-sufficient DTNs. Based on SARP, two multi-copy routing schemes are further developed to suit resource-limited DTNs, in which compensating the traffic demand become a challenge: i) the Self Adaptive Utility-based Routing Protocol (SAURP), ii) and the Adaptive Reinforcement based Routing Protocol (ARBRP). The introduced protocols form a new framework of DTNs aiming to significantly reduce the resource requirements of flooding-based routing schemes. Each introduced scheme has its own way of exploring the possibility of taking mobile nodes as message carriers in order to increase the delivery ratio of the messages. In SAURP, the best carrier for a message characterized by jointly considering the inter-contact time that is obtained using a novel contact model and the network status, such as including wireless link condition and nodal buffer availability. In ARBRP, the routing problem is solved by manipulating a collaborative reinforcement learning technique, where a group of nodes can cooperate with each other to make a forwarding decision for the stored messages based on a cost function at each contact with another node. ARBRP is characterized by not only considering the contact time statistics, but also looks into the feedback on user behavior and network conditions, such as congestion and buffer occupancy sampled during each previous contact with any other node. The thesis argues and proves that the nodal movement and the predicted collocation with the message recipient can serve as meaningful information to achieve an intelligent message forwarding decision at each node. Therefore, the introduced protocols can achieve high efficiency via an adaptive and intelligent routing mechanism according to network conditions. To fulfill the second objective, we further enhanced the performance of DTN routing by introducing message scheduling and dropping policies such that the delivery ratio is increased and/or the delivery delay is reduced. This thesis investigates new buffer management and scheduling policies to improve the performance of flooding and utility-based forwarding routing in DTNs, such that the forwarding/dropping decision can be made at a node during each contact for either optimal message delivery ratio or message delivery delay. To examine their effectiveness, the introduced protocols and the buffer management and scheduling policies have been implemented and compared to a number of existing counterpart approaches. A near-realistic mobility model is used for testing. A number of scenarios are used to evaluate the performance of the introduced techniques in terms of delivery delay, ratio, and the number of transmissions performed.
10

Topics in Delay Tolerant Networks (DTNs) : reliable transports, estimation and tracking / Transport fiable, estimation et poursuite dans les réseaux Delay Tolerant Networks (DTNs)

Ali, Arshad 12 November 2012 (has links)
Les réseaux mobiles Ad hoc (MANETs) visent à permettent à des noeuds mobiles de communiquer sans aucun support d'infrastructure. Les MANETs dispersés entrent dans la catégorie des réseaux tolérants aux délais (DTN), qui sont des réseaux connectés par intermittence et où il n'y a aucun chemin de bout-en-bout persistant à n'importe quel temps donné. Nous proposons, d'abord, un nouveau protocole de transport fiable pour les DTNs basé sur l'utilisation d'accusés de réception ainsi que le codage linéaire aléatoire. Nous modélisons l'évolution du réseau conformément à notre plan en utilisant l'approche fluide. Nous obtenons le temps de transfert d'un fichier en fonction de certains paramètres optimaux obtenus par l'approche d'évolution différentielle. Deuxièmement, Nous proposons ainsi et étudions un nouveau mécanisme d'ACK augmenté, pour améliorer le transport fiable pour les DTNs, pour les cas unicast et multicast. Nous nous servons du codage linéaire aléatoire aux relais pour que les paquets puissent atteindre la destination plus rapidement. Nous obtenons la fiabilité basée sur l'utilisation Global Sélective ACKnowledgement. Enfin, nous abordons le problème de l'estimation de propagation des fichiers dans les DTNs avec livraison directe et le routage épidémique. Nous estimons et suivons le degré de propagation d'un message dans le réseau. Nous fournissons la base analytique à notre cadre d'évaluation avec des aperçus validés en se basant sur des simulations. En plus, nous utilisons le filtre de Kalman et Minimum- Mean-Squared Error (MMSE) pour suivre le processus de propagation et trouvons que le filtre de Kalman fournit des résultats plus précis par rapport à MMSE / Mobile Ad hoc NETworks (MANETs) aim at making communication between mobile nodes feasible without any infrastructure support. Sparse MANETs fall into the class of Delay Tolerant Networks which are intermittently connected networks and where there is no contemporaneous end-to-end path at any given time. We first, propose a new reliable transport scheme for DTNs based on the use of ACKnowledgments and random linear coding. We model the evolution of the network under our scheme using a fluid-limit approach. We optimize our scheme to obtain mean file transfer times on certain optimal parameters obtained through differential evolution approach. Secondly, we propose and study a novel and enhanced ACK to improve reliable transport for DTNs covering both unicast and multicast flows. We make use of random linear coding at relays so that packets can reach the destination faster. We obtain reliability based on the use of so-called Global Selective ACKnowledgment. We obtain significant improvement through G-SACKs and coding at relays. Finally, we tackle the problem of estimating file-spread in DTNs with direct delivery and epidemic routing. We estimate and track the degree of spread of a message in the network. We provide analytical basis to our estimation framework alongwith insights validated with simulations. We observe that the deterministic fluid model can indeed be a good predictor with a large of nodes. Moreover, we use Kalman filter and Minimum- Mean-Squared-Error (MMSE) to track the spreading process and find that Kalman filter provides more accurate results as compared to MMSE

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