Resource Aware Application for Mobile Device In An Ad Hoc Wireless Network Environment

Ad hoc wireless networks can be applied in a collaborative computing in which the requirements of a temporary communication infrastructure for quick communication with minimal configuration between a group of people in a conference or gathering. The main purpose of this research is to develop an application that allows mobile nodes in a collaborative environment to share files among nodes. For this project, the application will be implemented on nodes in an ad hoc wireless network that have a strong incentive to collaborate and share resources. This paper presents the results of our preliminary study which are based on the previous research. It is divided into five sections where in the first section is an introduction of ad-hoc wireless network, then in the next section is regarding motivation of doing research in this area. In section four and five, the paragraphs focused on the evaluation for Mobile Ad Hoc Networking and related works respectively

Collaboration in Opportunistic Networks

Motivation. With the increasing integration of wireless short-range communication technologies (Bluetooth, 802.11b WiFi) into mobile devices, novel applications for spontaneous communication, interaction and collaboration are possible. We distinguish between active and passive collaboration. The devices help users become aware of each other and stimulate face-to-face conversation (active collaboration). Also, autonomous device communication for sharing information without user interaction is possible, i.e., devices pass information to other devices in their vicinity (passive collaboration). Both, active and passive collaboration requires a user to specify what kind of information he offers and what kind of information he is interested in. Object of Research: Opportunistic Networks. Spontaneous communication of mobile devices leads to so-called opportunistic networks, a new and promising evolution in mobile ad-hoc networking. They are formed by mobile devices which communicate with each other while users are in close proximity. There are two prominent characteristics present in opportunistic networks: 1) A user provides his personal device as a network node. 2) Users are a priori unknown to each other. Objectives. Due to the fact that a user dedicates his personal device as a node to the opportunistic network and interacts with other users unknown to him, collaboration raises questions concerning two important human aspects: user privacy and incentives. The users’ privacy is at risk, since passive collaboration applications may expose personal information about a user. Furthermore, some form of incentive is needed to encourage a user to share his personal device resources with others. Both issues, user privacy and incentives, need to be taken into account in order to increase the user acceptability of opportunistic network applications. These aspects have not been addressed together with the technical tasks in prior opportunistic network research. Scientific Contribution and Evaluation. This thesis investigates opportunistic networks in their entirety, i.e., our technical design decisions are appropriate for user privacy preservation and incentive schemes. In summary, the proposed concepts comprise system components, a node architecture, a system model and a simple one-hop communication paradigm for opportunistic network applications. One focus of this work is a profile-based data dissemination mechanism. A formal model for this mechanism will be presented. On top of that, we show how to preserve the privacy of a user by avoiding static and thus linkable data and an incentive scheme that is suitable for opportunistic network applications. The evaluation of this work is twofold. We implemented two prototypes on off-the-shelf hardware to show the technical feasibility of our opportunistic network concepts. Also, the prototypes were used to carry out a number of runtime measurements. Then, we developed a novel two-step simulation method for opportunistic data dissemination. The simulation combines real world user traces with artificial user mobility models, in order to model user movements more realistically. We investigate our opportunistic data dissemination process under various settings, including different communication ranges and user behavior patterns. Our results depict, within the limits of our model and assumptions, a good performance of the data dissemination process

On social and technical aspects of managing mobile Ad-hoc communities

Soziale Software beschreibt eine Klasse von Anwendungen, die es Benutzern erlaubt ueber das Internet mit Freunden zu kommunizieren und Informationen auszutauschen. Mit zunehmender Leistungsfaehigkeit mobiler Prozessoren verwandeln sich Mobiltelefone in vollwertige Computer und eroeffnen neue Moeglichkeiten fuer die mobile Nutzung sozialer Software. Da Menschen Mobiltelefone haeufig bei sich fuehren, koennen vergleichbare mobile Anwendungen staerker auf ihre unmittelbare Umgebungssituation zugeschnitten werden. Moegliche Szenarien sind die Unterstuetzung realer Treffen und damit verbundenen Mitgliederinteraktionen. Client-Server-Plattformen, die dabei haeufig zum Einsatz kommen wurden allerdings nie fuer solche hochflexiblen Gruppensituationen konstruiert. Mobile Encounter Netzwerke (MENe) verprechen hier mehr Flexibilitaet. Ein MEN stellt eine mobiler Peer-to-Peer-Plattformen dar, das ueber ein kurzreichweitiges Funknetz betrieben wird. Mit diesem Netzwerk werden Beitraege ueber einen raeumlichen Diffusionsprozess von einem mobilen Endgeraet zum naechsten verbreitet. Das hat zwei entscheidende Vorteile: Zunaechst ist der direkte Nachrichtenaustausch besser geeignet zur Verbreitung von situationsspezifischer Information, da die Informationsrelevanz mit ihrer Entfehrnung abnimmt. Gleichzeitig koennen aber auch Inhalte, die fuer einen breiten Interessenkreis bestimmt sind ueber Mitglieder mit herausragenden Mobilitaetscharakteristik in weit entfernte Gebiete transportiert werden. Ein Nachteil ist jedoch der hohe Ressourcenverbrauch. Zur Loesung dieses Problems entwickeln wir ein Rahmenwerk zur Unterstuetzung mobiler ad-hoc Gruppen, das es uns erlaubt, Gruppensynergien gezielt auszunutzen. Dieses Rahmenwerk bietet Dienstleistungen zur Verwaltung der Gruppendynamik und zur Verbreitung von Inhalten an. Mittels soziale Netzwerkanalyse wird die technische Infrastruktur ohne notwendige Benutzereingriffe kontinuierlich an die reale Umgebungssituation angepasst. Dabei werden moegliche Beziehungen zwischen benachbarten Personen anhand frueher Begegnungen analysiert, spontane Gruppenbildungen mit Clusterverfahren identifiziert und jedem Gruppenmitglied eine geeignete Rolle durch eine Positionsanalyse zugewiesen. Eine Grundvorraussetzung fuer eine erfolgreiche Kooperation ist ein effizienter Wissensaustausch innerhalb einer Gemeinschaft. Wie die Small World-Theorie zeigt, koennen Menschen Wissen auch dann effizient verbreiten, wenn ihre Entscheidung nur auf lokaler Umgebungsinformation basiert. Verschiedene Forscher machten sich das zu nutze, indem sie kurze Verbreitungspfade durch eine Verkettung hochvernetzter Mitglieder innerhalb einer Gemeinschaft konstruierten. Allerdings laesst sich dieses Verfahren nicht einfach auf MENe uebertragen, da die Transferzeit im Gegensatz zu dem drahtgebundenen Internet beschraenkt ist. Unser Ansatz beruht daher, auf der von Reagan et al. vorgestellten Least Effort Transfer-Hypothese. Diese Hypothese besagt, dass Menschen Wissen nur dann weitergeben, wenn sich der Aufwand zur Informationsuebertragung innerhalb bestimmter Grenzen bewegt. Eine erfolgreiche Wissensuebertragung haengt in diesem Fall vom Hintergrundwissen aller Beteiligter ab, was wiederum von unterschiedlichen kognitiven und sozialen Faktoren abhaengt. Entsprechend leiten wir ein Diffusionsverfahren ab, dass in der Lage ist, Inhalte in verschiedene Kompexitaetstufen einzuteilen und Datenuebertragungen an die vorgefundene soziale Situation anzupassen. Mit einem Prototyp evaluieren wir die Machbarkeit der Gruppen- und Informationsmanagementkomponente unseres Rahmenwerkes. Da Laborexperimente keinen ausreichenden Aufschluss ueber Diffusionseigenschaften im groesseren Massstab geben koennen, simulieren wir die Beitragsdiffusion. Dazu dient uns eine Verkehrsimulation, bei der Agenten zusaetzlich mit aktivitaetsbezogenen, sozialen und territorialen Modellen erweitern werden. Um eine realitaetsnahe Simulation zu gewaehrleisten, werden diese Modelle in Uebereinstimmung mit verschiedenen Studien zum Stadtleben generiert. Der technische Uebertragungsprozess wird anhand der Ergebnisse einer vorangegangenen Prototypuntersuchung parametrisiert. Waehrend eines Simulationslaufes bewegen sich Agenten auf einem Stadtplan und sammeln Kontakt- und Beitragsdaten. Analysiert man anschliessend die Netzwerktopologie auf Small World-Eigenschaften, so findet man eine Netzstruktur mit einer ausgepraegten Neigung zum Clustering (Freundschaftsnetzwerke) und einer ueberdurschnittlichen kurzen Weglaenge. Offensichtlich reicht die Alltagsmobilitaet aus, um ausreichend viele Verknuepfungen zwischen Gemeinschaftmitgliedern zu bilden. Die nachfolgende Diffusionsanalyse zeigt, dass vergleichbare Reichweiten wie bei einem flutungsbasierten Ansatz erzielt werden, allerdings mit anfaenglichen Verzoegerungen. Da unser Verfahren bei einem Ortswechsel die Anzahl der Informationsuebermittler auf zentrale Gruppenmitglieder begrenzt, steht mehr Bandbreite fuer den Datenaustausch zur Verfuegung. Herkoemliche Mitglieder (ohne Leitungsaufgaben) tauschen Inhalte vornehmlich in zeitunkritschen Situationen aus. Das hat den positiven Nebeneffekt, dass im Cache erheblich weniger Kopien aussortiert werden muessen. Wechselt man waehrend der Simulation die Beitragskategorie so erkennt man, dass zeitabhaengige Inhalte besser ueber regelmaessige Kontakte und zeitunabhaengig Inhalte durch zufaellige Kontakte verbreitet werden. Eine abschliessende Precision-Recall Analyse zeigt, dass herkoemmliche Gruppenmitglieder eine bessere Genauigkeit (Precision), und zentrale Mitglieder eine bessere Trefferquote (Recall) im Vergleich zu traditionellen Ansaetzen besitzen. Eine Erklaerung dafuer ist, dass der von uns gewaehlte gruppenbasierte Cacheansatz zu weniger Saeuberungszyklen aller Gruppenmitglieder fuehrt und somit nachhaltiger ausgerichtet ist.Social software encompasses a range of software systems that allow users to interact and share data. This computer-mediated communication has become very popular with social networking sites like Facebook and Twitter. The evolvement of smart phones toward mobile computers opens new possibilities to use social software also in mobile usage scenarios. Since mobile phones are permanently carried by their owners, the support focus is, however, much stronger set on promoting and augmenting real group gatherings. Traditional client-server platforms are not flexible enough to support complex and dynamic human encounter behavior. Mobile encounter networks (MENs) which represent a mobile peer-to-peer platform on top of a short range wireless network promise better flexibility. MENs diffuse content from neighbor-to-neighbor in a spatial diffusion process. For physical group gatherings this is advantageous for two reasons. Direct device-to-device interactions encourage sharing of situation-dependent content. Moreover, content is not necessarily locked within friend groups and may trigger networking effects by reaching larger audiences through user mobility. One disadvantage is, however, the high resource usage. We develop a social software framework for mobile ad-hoc groups, which partly solves this problem. This framework supports services for the management of group dynamics and content diffusion within and between groups. Social network analysis as an inherent part of the framework is used to adapt internal community states continuously with real world encounter situations. We hereby qualify interpersonal relationships based on encounter and communication statistics, identify social groups through incremental clustering and assign diffusion roles through position analysis. To achieve efficient content dissemination we make use of social diffusion phenomena. Other researchers have experimented extensively with the small world model as it proofs that people transfer knowledge based on local knowledge but are still capable of diffusing it efficiently on a global scale. Their approach is often based on identifying short paths through member connectivity. However, this scenario is not applicable in MENs as transfer time is limited in contrast to the wired Internet. Our approach is therefore based on the least effort transfer theory. Following Reagan et al., who first postulated this hypothesis, people transfer knowledge only if the transfer effort is within specific limits, which depends on different social and cognitive factors. We derive routing mechanisms, which are capable of distinguishing between different content complexities and apply information about peer's expertise and social network to identify advantageous paths and content transfers options. We evaluate the feasibility of the group management and content transfer component with prototypes. Since labor settings do not allow to obtain information about large scale diffusion experiences, we also conduct a multi-agent simulation to evaluate the diffusion capabilities of the system. Experiences from an earlier prototype implementation have been used to quantify the technical routing process. To emulate realistic community life, we assigned to each agent an individual daily agenda, social contacts and territory preferences specified according to outcomes from different urban city life surveys. During the simulation agents move on a city map according to these models and collect contact and content specific data. Analyzing the network topology according to small world characteristics shows a structure with a high tendency for clustering (friend networks) and a short average path length. Daily urban mobility creates enough opportunities to form shortcuts through the community. Content diffusion analysis shows that our approach reaches a similar amount of peers as network flooding but with delays in the beginning. Since our approach artificially limits the number of intermediates to central community peers more bandwidth is available during traveling and more content can be transferred as in the case of the flooding approach. Ordinary peers seem to have significantly fewer content replications if an unlimited cache is assumed proofing that our mechanism is more efficient. By varying the content type used during the simulation we recognize that time dependent content is better disseminated through frequent contacts and time independent content through random contacts. Performing a precision-recall analysis on peers caches shows that ordinary peers gain an overall better context precision, and central peers a better community recall. One explanation is that the shared cache approach leads to fewer content replacements in the cache as for instance the least recently used cache strategy

Application Platforms, Routing Algorithms and Mobility Behavior in Mobile Disruption-Tolerant Networks

Mobile disruption-tolerant networks (DTNs), experience frequent and long duration partitions due to the low density of mobile nodes. In these networks, traditional networking models relying on end-to-end communication cease to work. The topological characteristics of mobile DTNs impose unique challenges for the design and validation of routing protocols and applications. We investigate challenges of mobile DTNs from three different viewpoints: the application layer, a routing perspective, and by studying mobility patterns. In the application layer, we have built 7DS (7th Degree of Separation) as a modular platform to develop mobile disruption-tolerant applications. 7DS offers a class of disruption-tolerant applications to exchange data with other mobile users in the mobile DTN or with the global Internet. In the routing layer, we have designed and implemented PEEP as an interest-aware and energy efficient routing protocol which automatically extracts individual interests of mobile users and estimates the global popularity of data items throughout the network. PEEP considers mobile users' interests and global popularity of data items in its routing decisions to route data toward the community of mobile users who are interested in that data content. Mobility of mobile users impacts the conditions in which routing protocols for mobile DTNs must operate and types of applications that could be provided for mobile networks in general. The current synthetic mobility models do not reflect real-world mobile users' behavior. Trace-based mobility models, also, are based on traces that either represent a specific population of mobile users or do not have enough granularities in representing mobility of mobile users for example cell tower traces. We use Sense Networks' GPS traces that are being collected by monitoring a broad spectrum of mobile users. Using these traces, we employ a Markovian approach to extract inherent patterns in human mobility. We design and implement a new routing algorithm for mobile DTNs based on our Markovian analysis of the human mobility. We explore how the knowledge of the mobility improves the performance of our Markov based routing algorithm. We show that that our Markov based routing algorithm increases the rate of data delivery to popular destinations with consuming less energy than legacy algorithms

A mixed methods study of online course facilitators\u27 perceptions of mobile technology, design, and TPaCK affordances

The increase in mobile technology options for students in post-secondary, continuing education influences how instructors design and implement courses, specifically online courses (Sözcü, İpek, & Kınay, 2016). Much of the current research addresses technological, pedagogical, and content knowledge (TPaCK), course design, and/or mobile technology as separate topics. There is limited research addressing the combination of TPaCK, design, and mobile technology from the course instructors’ perspective. The mixed methods study addressed design for online, mobile learning with a new layer of the TPaCK instructional framework in three phases. Phase 1 involved a pilot study of a survey that measured TPaCK, lesson design practices, and design perceptions. The pilot study responses informed Phase 2. In Phase 2, the survey was given to 33 current online course facilitators from PBS TeacherLine, an online continuing education course provider. Responses were gathered. In Phase 3, a qualitative interview designed to understand online course instructors’ perceptions of their use of mobile technology, design decisions, and the TPaCK, instructional framework was conducted with a random sample of twelve people from the survey participant pool. The threefold data collection process allowed for a triangulation of the findings, which heightened construct validity and comprehensive understanding. In Finding 1, 100% of the online continuing education course facilitators integrated TPaCK in their courses through the use of mobile and digital tools. In Finding 2, 100% of the online continuing education course facilitators made dynamic and innovative mobile and digital design decisions through the creation of supplemental course content. In Finding 3, 92% of online continuing education course facilitators utilized mobile technology in their online courses through an innovative inclusion of both mobile devices and mobile apps. Five conclusions resulted from the study and are discussed. The study contributes to existing literature by providing a 6-point effectiveness checklist, with the acronym “SCROLL” to operationalize for the professional development of pre-service and current online course facilitators

Improving Content Delivery and Service Discovery in Networks

Production and consumption of multimedia content on the Internet is rising, fueled by the demand for content from services such as YouTube, Netflix and Facebook video. The Internet is shifting from host-based to content-centric networking. At the same time, users are shifting away from a homogeneous desktop computing environment to using a heterogeneous mix of devices, such as smartphones, tablets and thin clients, all of which allow users to consume data on the move using wireless and cellular data networks. The popularity of these new class of devices has, in turn, increased demand for multimedia content by mobile users. The emergence of rich Internet applications and the widespread adoption and use of High Definition (HD) video has also placed higher pressure on the service providers and the core Internet backbone, forcing service providers to respond to increased bandwidth use in such networks. In my thesis, I aim to provide clarity and insight into the usage of core networking protocols and multimedia consumption on both mobile and wireless networks, as well as the network core. I also present research prototypes for potential solutions to some of the problems caused by the increased multimedia consumption on the Internet

Kooperative Angriffserkennung in drahtlosen Ad-hoc- und Infrastrukturnetzen: Anforderungsanalyse, Systementwurf und Umsetzung

Mit der zunehmenden Verbreitung mobiler Endgeräte und Dienste ergeben sich auch neue Herausforderungen für ihre Sicherheit. Diese lassen sich nur teilweise mit herkömmlichen Sicherheitsparadigmen und -mechanismen meistern. Die Gründe hierfür sind in den veränderten Voraussetzungen durch die inhärenten Eigenschaften mobiler Systeme zu suchen. Die vorliegende Arbeit thematisiert am Beispiel von Wireless LANs die Entwicklung von Sicherheitsmechanismen für drahtlose Ad-hoc- und Infrastrukturnetze. Sie stellt dabei den umfassenden Schutz der einzelnen Endgeräte in den Vordergrund, die zur Kompensation fehlender infrastruktureller Sicherheitsmaßnahmen miteinander kooperieren. Den Ausgangspunkt der Arbeit bildet eine Analyse der Charakteristika mobiler Umgebungen, um grundlegende Anforderungen an eine Sicherheitslösung zu identifizieren. Anhand dieser werden existierende Lösungen bewertet und miteinander verglichen. Der so gewonnene Einblick in die Vor- und Nachteile präventiver, reaktiver und angriffstoleranter Mechanismen führt zu der Konzeption einer hybriden universellen Rahmenarchitektur zur Integration beliebiger Sicherheitsmechanismen in einem kooperativen Verbund. Die Validierung des Systementwurfs erfolgt anhand einer zweigeteilten prototypischen Implementierung. Den ersten Teil bildet die Realisierung eines verteilten Network Intrusion Detection Systems als Beispiel für einen Sicherheitsmechanismus. Hierzu wird eine Methodik beschrieben, um anomalie- und missbrauchserkennende Strategien auf beliebige Netzprotokolle anzuwenden. Die Machbarkeit des geschilderten Ansatzes wird am Beispiel von infrastrukturellem WLAN nach IEEE 802.11 demonstriert. Den zweiten Teil der Validierung bildet der Prototyp einer Kooperations-Middleware auf Basis von Peer-to-Peer-Technologien für die gemeinsame Angriffserkennung lose gekoppelter Endgeräte. Dieser kompensiert bisher fehlende Mechanismen zur optimierten Abbildung des Overlay-Netzes auf die physische Struktur drahtloser Netze, indem er nachträglich die räumliche Position mobiler Knoten in die Auswahl eines Kooperationspartners einbezieht. Die zusätzlich definierte Schnittstelle zu einem Vertrauensmanagementsystem ermöglicht die Etablierung von Vertrauensbeziehungen auf Kooperationsebene als wichtige Voraussetzung für den Einsatz in realen Umgebungen. Als Beispiel für ein Vertrauensmanagementsystem wird der Einsatz von Reputationssystemen zur Bewertung der Verlässlichkeit eines mobilen Knotens diskutiert. Neben einem kurzen Abriss zum Stand der Forschung in diesem Gebiet werden dazu zwei Vorschläge für die Gestaltung eines solchen Systems für mobile Ad-hoc-Netze gemacht.The increasing deployment of mobile devices and accompanying services leads to new security challenges. Due to the changed premises caused by particular features of mobile systems, these obstacles cannot be solved solely by traditional security paradigms and mechanisms. Drawing on the example of wireless LANs, this thesis examines the development of security mechanisms for wireless ad hoc and infrastructural networks. It places special emphasis on the comprehensive protection of each single device as well as compensating missing infrastructural security means by cooperation. As a starting point this thesis analyses the characteristics of mobile environments to identify basic requirements for a security solution. Based on these requirements existing preventive, reactive and intrusion tolerant approaches are evaluated. This leads to the conception of a hybrid and universal framework to integrate arbitrary security mechanisms within cooperative formations. The resulting system design is then validated by a twofold prototype implementation. The first part consists of a distributed network intrusion detection system as an example for a security mechanism. After describing a methodology for applying anomaly- as well as misuse-based detection strategies to arbitrary network protocols, the feasibility of this approach is demonstrated for IEEE 802.11 infrastructural wireless LAN. The second part of the validation is represented by the prototype of a P2P-based cooperation middleware for collaborative intrusion detection by loosely coupled devices. Missing mechanisms for the improved mapping of overlay and physical network structures are compensated by subsequently considering the spatial position of a mobile node when choosing a cooperation partner. Furthermore, an additional interface to an external trust management system enables the establishment of trust relationships as a prerequisite for a deployment in real world scenarios. Reputation systems serve as an example of such a trust management system that can be used to estimate the reliability of a mobile node. After outlining the state of the art, two design patterns of a reputation system for mobile ad hoc networks are presented

Connecting through smartphones: Cognitive, social, emotional motivations, and the experience of value perceptions

Smartphones became a dominant medium for communication with the emergence of converging technology. Since smartphones enable people to access various services, and to interact with other people within mobile social networks, users have become highly involved with such devices. To understand motivational factors associated with using smartphone, this study was informed by perceived cognition (i.e., expected outcomes) and social influence (i.e., social identity) from a social cognitive perspective, which was expanded to incorporate the dimension of emotional attachment. To develop its “motivational framework”, this study adopted social cognitive theory and attachment theory. This study also investigated the “experience of value perceptions” (i.e., perceived social, hedonic, and utilitarian values) that emerged concurrently with smartphone use. Moreover, consumption value theory was employed to understand the perceived values of smartphone users. Ultimately, a Motivation-Experience-Behavior (M-E-B) model was suggested for smartphone users. The main purpose of this study is to examine how different motivations influence perceived values of using the device, which consequently explains current smartphone use. Structural equation modeling (SEM) was used to test the proposed model. Data collected from 738 current smartphone users was analyzed. Regarding results, cognitive factors (i.e., information seeking, entertained activity, and self-reactiveness), and social influence (i.e., SNS social identity) explained value perceptions (i.e., social, hedonic, and utilitarian values). Expectations of social contact, however, did not explain value perception (i.e., social value). Effects of emotional attachment on value perceptions (i.e., social, hedonic, and utilitarian values) were detected. Consequently, perceived values influenced recent use of the smartphone. In addition, demographic differences (e.g., age, sex, socioeconomic status, and race) as regards such motivations were found, and demographic variables were further included in the model as control variables. Last, to examine sex differences in the hypothesized model, two different sex groups were compared. In the male group, motivation of entertainment activity did not explain hedonic value perception, and experiences of social and hedonic values importantly explained use of the smartphone. In the female group, motivation of self-reactiveness did not have an effect on hedonic value perception, and experiences of social and functional values had an effect on use of the smartphone

Secure, Efficient and Privacy-aware Framework for Unstructured Peer-to-Peer Networks

Recently, the advances in Ubiquitous Computing networks and the increased computational power of network devices have led designers to create more flexible distributed network models using decentralised network management systems. Security, resilience and privacy issues within such distributed systems become more complicated while important tasks such as routing, service access and state management become increasingly challenging. Low-level protocols over ubiquitous decentralised systems, which provide autonomy to network nodes, have replaced the traditional client-server arrangements in centralised systems. Small World networks represent a model that addresses many existing challenges within Ubiquitous Computing networks. Therefore, it is imperative to study the properties of Small World networks to help understanding, modelling and improving the performance, usability and resiliency of Ubiquitous Computing networks. Using the network infrastructure and trusted relationships in the Small World networks, this work proposes a framework to enhance security, resilience and trust within scalable Peer-to-Peer (P2P) networks. The proposed framework consists of three major components namely network-aware topology construction, anonymous global communication using community trust, and efficient search and broadcasting based on granularity and pro-active membership management. We utilise the clustering co-efficient and conditional preferential attachment to propose a novel topology construction scheme that organises nodes into groups of trusted users to improve scalability. Network nodes communicate locally without advertising node identity at a global scale, which ensures user anonymity. The global communication is organised and facilitated by Service Centres to maintain security, privacy and integrity of member nodes. Service Centres are allocated using a novel leader election mechanism within unstructured scalable P2P networks. This allows providing fair and equitable access for existing and new nodes without having to make complex changes to the network topology. Moreover, the scale-free and clustering co-efficient characteristics of Small World networks help organising the network layout to maintain its balance in terms of the nodes distribution. Simulation results show that the proposed framework ensures better scalability and membership management in unstructured P2P networks, and improves the performance of the search and broadcasting in terms of the average shortest path and control overhead while maintaining user anonymity and system resiliency

PRSONA: Private Reputation Supporting Ongoing Network Avatars

Trust and user-generated feedback have become increasingly vital to the normal functioning of the modern internet. However, deployed systems that currently incorporate such feedback do not guarantee users much in the way of privacy, despite a wide swath of research on how to do so spanning over 15 years. Meanwhile, research on systems that maintain user privacy while helping them to track and update each others' reputations has failed to standardize terminology, or converge on what privacy guarantees should be important. Too often, this leads to misunderstandings of the tradeoffs underpinning design decisions. Further, key insights made in some approaches to designing such systems have not circulated to other approaches, leaving open significant opportunity for new research directions. Acknowledging this situation, online communities in particular face a difficult dilemma. Communities generally want to provide opportunities for their members to interact and communicate with one another in ways that advance their mutual interests. At times, communities may identify opportunities where providing their members specific privacy guarantees would particularly aid those opportunities, giving members assurances that their participation would not have negative consequences for themselves. However, communities also face the threat of bad actors, who may wish to disrupt their activities or bring harm to members for their status as members of such groups. The privacy that the community wishes to extend to members must be carefully approached so that bad actors can still be held accountable. This thesis proceeds in two parts. First, this thesis investigates 47 systems describing privacy-preserving reputation systems from 2003--2021 in order to organize previous work and suggest directions for future work. The three key contributions in this portion of the thesis are the systematization of this body of research, the detailing of the tradeoffs implied by overarching design choices, and the identification of underresearched areas that provide promising opportunities for future work. Second, this thesis explores one particular opportunity for new research identified in the first section of the thesis. Whereas previous work has overlooked the needs of certain kinds of small, tight-knit communities, this work features a novel design for a privacy-preserving reputation system that is targeted to fill that gap. The nature of its design is discussed particularly in contrast to the identified patterns of design present in previous works. Further, this thesis implements and benchmarks said system to determine its viability in real-world deployment. This novel construction addresses shortcomings with previous approaches and provides new opportunities for its intended audiences