ABSTRACT
This research work presents the development of a privacy aided trust routing model using social similarity in an Opportunistic Network (OppNet). OppNet is a delay tolerant network where link is highly unpredictable. It is an ideal solution in situations where the deployment of wired and conventional wireless networks is difficult or practically impossible. However, OppNet is faced with several challenges. Most of these challenges are related to routing, buffer management or security. The most promising amongst the several approaches by researchers at addressing these challenges are the ones that explored social behavior of human beings. The mobile nature of OppNets however brought to the fore the need for a more efficient and effective security model. This work, therefore, intends to further strengthen privacy in an OppNet. This is done by developing a community-based privacy preservation scheme using a symmetric cryptographic model, based on a differential equation of a curvi-circular function by applying Galois theory. The key distribution is made possible by partial application of onion routing scheme. The developed privacy scheme is incorporated into trust routing based on social similarity (TRSS) to become Privacy Aided TRSS (PATRSS). This approach improves the security in terms of preservation of privacy of messages and that of the relay nodes without compromising other network performance indicators. Using metrics, such as delivery ratio, delivery cost and average trust performance, PATRSS is simulated on Opportunistic Network Environment (ONE) simulator. PATRSS out performed TRSS by 7.8%, 30.7% and 9.4% in terms of delivery ratio, delivery cost and average trust value respectively. Finally, the TRSS and PATRSS which are originally routed on spray and wait routing algorithm are implemented on Epidemic, PRoPHET and MaxProp. Using numbers of messages duplicated, those aborted and those delivered as metrics, the results are presented to clearly show the network performance, the improvements, and the costs. These demonstrate the effectiveness and the efficiency of PATRSS.
TABLE OF CONTENTS
DECLARATION …………………………………………………………………………………………………………… i
CERTIFICATION ………………………………………………………………………………………………………… ii
DEDICATION …………………………………………………………………………………………………………….. iii
ACKNOWLEDGEMENT …………………………………………………………………………………………….. iv
ABSTRACT ………………………………………………………………………………………………………………….. v
LIST OF FIGURES ……………………………………………………………………………………………………… ix
LIST OF TABLES ………………………………………………………………………………………………………… x
LIST OF ABBREVIATIONS ……………………………………………………………………………………….. xi
CHAPTER ONE …………………………………………………………………………………………………………… 1
INTRODUCTION ………………………………………………………………………………………………………… 1
1.1 Background to Study …………………………………………………………………………………………… 1
1.2 Significance of Research ……………………………………………………………………………………… 3
1.3 Problem Statement ……………………………………………………………………………………………… 4
1.4 Aim and Objectives …………………………………………………………………………………………….. 5
1.5 Motivation …………………………………………………………………………………………………………. 6
1.6 Thesis Organization…………………………………………………………………………………………….. 6
CHAPTER TWO ………………………………………………………………………………………………………….. 7
LITERATURE REVIEW ……………………………………………………………………………………………… 7
2.1 Introduction ……………………………………………………………………………………………………… 7
2.2 Review of Fundamental Concepts……………………………………………………………………….. 7
2.2.1 Opportunistic Network ………………………………………………………………………………….. 7
2.2.2 Classification of opportunist network routing protocols …………………………………… 16
2.3 Opportunistic Network Environment Simulator ……………………………………………………. 22
2.4 Network Security and Privacy…………………………………………………………………………….. 24
2.4.1 Onion Routing ……………………………………………………………………………………………. 27
2.5 Fundamentals of Galois Theorem ……………………………………………………………………….. 28
2.5.1 Groups and group theory ……………………………………………………………………………… 28
2.5.2 Symmetric groups ……………………………………………………………………………………….. 29
2.5.3 Rings and polynomials ………………………………………………………………………………… 31
2.5.4 The galois theorem ……………………………………………………………………………………… 31
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2.6 Review of Similar Works …………………………………………………………………………………… 32
CHAPTER THREE …………………………………………………………………………………………………….. 42
METHODS AND MATERIALS ………………………………………………………………………………….. 42
3.1 Introduction ……………………………………………………………………………………………………… 42
3.2 Methodology ……………………………………………………………………………………………………. 42
3.3 Datasets and Trust Model …………………………………………………………………………………… 44
3.4 Trust Routing……………………………………………………………………………………………………. 45
3.5 Development of Privacy Preservation ………………………………………………………………….. 46
3.5.1 Development of message privacy ………………………………………………………………….. 46
3.5.2 Development of relay node’s privacy …………………………………………………………….. 50
3.6 Incorporation of Privacy into trust routing ……………………………………………………………. 51
3.7 Modelling The Datasets …………………………………………………………………………………….. 54
3.8 Model Test Case ……………………………………………………………………………………………….. 54
3.8.1 Simulations ……………………………………………………………………………………………………. 55
3.8.2 Validating of PATRSS in epidemic PRoPHET and MaxProp ………………………………. 57
CHAPTER FOUR ……………………………………………………………………………………………………….. 58
RESULTS AND DISCUSSION ……………………………………………………………………………………. 58
4.1 Introduction ……………………………………………………………………………………………………… 58
4.2 Dataset Modelling …………………………………………………………………………………………….. 58
4.3 Performance of PATRSS in Terms of Delivery Ratio ……………………………………………. 59
4.4 Performance of PATRSS in Terms of Delivery Cost …………………………………………….. 60
4.5 Performance of PATRSS in Terms of Average Trust Value …………………………………… 62
4.7 Validation of PATRSS with Common Routing Protocols ……………………………………….. 64
CHAPTER FIVE ………………………………………………………………………………………………………… 68
CONCLUSION AND RECOMMENDATIONS ……………………………………………………………. 68
5.1 Introduction ……………………………………………………………………………………………………… 68
5.2 Summary …………………………………………………………………………………………………………. 68
5.3 Conclusion ……………………………………………………………………………………………………….. 68
5.4 Contribution to Knowledge ………………………………………………………………………………… 68
5.5 Recommendations for Further Work……………………………………………………………………. 69
REFERENCE ……………………………………………………………………………………………………………… 70
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Appendix …………………………………………………………………………………………………………………….. 82
CHAPTER ONE
INTRODUCTION
1.1 Background to the Study
An opportunistic network (OppNet) is a type of Delay Tolerant Network (DTN) and an evolution of Mobile Ad-hoc Network (MANET) in which a message can be transferred from source to destination even if a continuous connection from source to destination does not exist at an instance of time. Therefore, it utilizes and relies upon the opportunistic pair-wise contact between nodes in the network. Thus, messages are routed (or forwarded) from one node to another at any point in time they are close enough within the very limited wireless range of each other. This may happen repeatedly, so that eventually, the message gets to the destination. Thus, it uses store-carry-forward networking paradigm (C’amara et al., 2011; Musolesi & Mascolo, 2008). Figure 1.1 illustrates how a message is forwarded hop by hop by the relay nodes from a source node to the destination node.
Figure 1. 1: Message Forwarding in OppNet (Noorin, 2009)
Due to the fact that OppNets can be used where there is no network infrastructure, thus having high scalability, it finds applications in many areas such as ubiquitous computing, disaster
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management, military surveillance and battle field, wildlife monitoring and Eco-physiology, Vehicular Ad-hoc Networks (VANET’s), Internet of Things (IoT), deep space exploration, etc. (Luo et al., 2008; Malladi & Agrawal, 2002; NASA, 2012). Despite OppNets being a potential solution to some of the problems of the traditional networks; the frequent disruption, long delay, dynamic and ad-hoc (self-organising) nature of OppNets present some challenges that need to be overcome in order to optimally reap its usefulness. Researches in OppNets cut across disciplines related to computer networking (computer science and engineering), mathematics, information sciences, and social sciences (sociology and social psychology).
Recently, research interests on OppNets have grown because it is a promising solution to the limits of the traditional infrastructure-based networks. Researchers have done a lot of work on areas related to the routing protocols. Since OppNets use store-carry-forward network paradigm, the buffer management is also a very important aspect of the network. For this, many in-depth works have also been reported on the buffer management strategies (Viscal et al., 2014; Pan et al., 2013). The wireless devices in this network that help route messages may be held by humans, attached to animals, or part of transport systems such as: vehicles, ships, airplanes, amongst others (Balasubramanian et al., 2008; Eagle & Pentland, 2006; McNett & Voelker, 2005). These devices do not just buffer the message but also carry it as they move in the environment until they have pair-wise encounter with the destination or more suitable relay nodes towards the destination. Therefore, the mobility of the carriers of these devices impacts greatly on the performance of OppNets (Camp et al., 2002; Karamshuk et al., 2011; Lin et al., 2004). As such, studies have also been made on this aspect so as to improve the performance of the network. In addition, data from real life contact traces have been gathered in efforts to make an OppNet a reality (Henderson et al. 2004; Mtibaa et al., 2008; Piorkowski et al., 2009).
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More recently, behavioral pattern of humans from their social interactions in terms of connectivity and mobility has been researched. The social interaction includes: residence, friends, place of work, etc. Others uses behavioral pattern that is related to interest, centrality, community, proximity, amongst others (D’ora & Holezer, 2010; Hui et al., 2011; Fan et al., 2013; Daly et al., 2009; Abdelkader et al., 2013). The behavioral pattern of the social interactions has been identified as the most promising means of routing in many researches (Zhang et al., 2014; Zhou et al., 2013; Usman & Gutierrez, 2018). Thus, because nodes in OppNet are mobile and ‘social’ sine qua non, (i.e. mobility and social interaction cannot be completely separated in real life), it is also called Opportunistic Mobile Social Networks (OMSN).
However, despite all these works, the usefulness of OppNet’s is limited without a serious consideration to the issues of security and privacy (Liang et al., 2013; Kumar et al., 2018; Liu et al., 2018). Because of the nature of OppNets, there is trade-off between routing efficiency and privacy as presented by Costantino et al., (2014). Hence, the need for more thorough and realistic works on this aspect of OppNet.
1.2 Significance of Research
This research work proposes development of a scheme that incorporates privacy preservation in opportunistic network (OppNet) with trust routing. This scheme combines the cryptographic security mechanisms with the key distribution by means of partial onion routing protocol to ensure both the privacy of message and that of the relay nodes are preserved. Without such scheme, the willingness of some potential nodes to participate in the routing/forwarding of messages cannot be realized as a node may not be willing to share its social information which could be very vital in choosing suitable relay nodes. Since message routing/forwarding in OppNet utilizes opportunistic contact of nodes, this causes considerable degradation in performance. Furthermore, if malicious
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and selfish nodes are present in the network, they have the potential to harm the cooperative nodes that willingly share their information in the absence of privacy before they are detected by the trust and feedback mechanisms of trust routing.
With privacy preservation the opportunistic contacts of nodes are better utilized. This is because trust ensures communication between nodes that have prior knowledge of each other. Privacy preservation ensures communication between nodes even in the absence of any prior knowledge. Privacy preservation gives a new “unknown” and a “repented” misbehaving (non-cooperating) node better opportunity to join the co-operative nodes in the network and the chance to build a trust profile with time.
In addition, if the sensitivity of a message to be sent requires a node of high trust value, and the number of such nodes is not much in the network, then the cost of getting such message to the destination becomes prohibitively high. This is because such message is kept in the buffer for a very long time and continually duplicated many times so that it is not lost if the message time to live (TTL) expired. Without a scheme such as privacy preservation in trust routing, transmitting sensitive message through the network incurs very high cost.
1.3 Problem Statement
According to Yao et al., (2016), the thrust management model using social similarity performs greatly in securing an opportunistic network against malicious and selfish nodes. This is possible in an ideal scenario where the privacy of the messages been sent does not matter and the relay nodes are willing to share their social information, which helps in the routing, without worrying about their privacy. This ideal case deviates greatly from the reality.
Firstly, this is because such ideal scenarios are only possible in the presence of relay nodes that corporate without worrying about their privacy. Secondly, in a highly challenged, sparse or dense
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environment, the nodes may completely be unaware of each other prior to their meeting, yet the need for opportunistic transfer of messages can arise which is the core importance of OppNets. Thirdly, trust routing impacts negatively on the delivery probability. This is due to the fact that the more trust a node demands (for a sensitive message) the less the delivery rate that can be achieved as few numbers of nodes can meet such condition. On the other hand, the lesser the trust level a node demands for routing the easier its security is compromised.
One of the main problems with trust models in OppNets is its inability to effectively utilize the contact opportunities with new nodes for message routing/forwarding. This seriously reduces the delivery rate because OppNet relies mainly on opportunistic contacts between nodes for message delivery.
By incorporating privacy preservation into the trust routing the security and the routing performance can be improved simultaneously. This is because; presence of privacy protection allows the nodes to mutually help one another in the routing/forwarding of messages even before significant trust is established. Furthermore, mutual interaction of a node with an “unknown” node facilitates the establishment of the trust. Consequently, the negative effects of trust routing on message delivery in OppNets is mitigated.
1.4 Aim and Objectives
The aim of this research is to develop a privacy-aided trust routing based on social similarity in opportunistic network.
The objectives are to:
1. Develop a community-dependent privacy scheme.
2. Incorporate the developed privacy into Trust Routing Based on Social Similarity (TRSS) to form privacy aided TRSS (PATRSS)
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3. Compare the performance of PATRSS with Privacy in OppNet (PO) and TRSS in terms of delivery ratio, delivery cost, and trust performance.
1.5 Motivation
It is estimated that there are over 3.3 billion mobile phone users around the world. This number is more than a half of the world population. Utilizing the wireless, processing and buffering capabilities of mobile phones and other wireless devices in Opportunistic Network (OppNet) is a promising solution to some of the limits which the traditional infrastructure-based imposed on wireless communications. Although many approaches are proposed, trust based social-aware OppNets have been shown to perform significantly better than others.
However, the basic assumptions upon which trust routings are built limits its usefulness in many applications. This means that, by developing a scheme to mitigate the consequences of these assumptions, the usefulness of OppNets is significantly improved.
1.6 Thesis Organization
Chapter One of this thesis gives background information of this research. Chapter Two follows by providing the review of literatures related to the fundamental concepts on this research and those related to past works on trust routing in OppNets. Thereafter, Chapter Three expatiate on the materials and methods adopted for the success of this work. In addition, Chapter Four presents the results and discusses them. This leads to conclusion and recommendations that are discussed in Chapter Five. And finally, quoted references and appendices are provided at the end of this thesis.
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