Security is essential to communication between entities in the internet. Delay tolerant and disconnected Mobile Ad Hoc Networks (MANET) are a class of networks characterized by high end-to-end path latency and frequent end-to-end disconnections and are often termed as challenged networks. In these networks nodes are sparsely populated and without the existence of a central server, acquiring global information is difficult and impractical if not impossible and therefore traditional security schemes proposed for MANETs cannot be applied. This thesis reports trust management schemes for peer to peer (P2P) application in delay tolerant disconnected MANETs. Properties of a profile based file sharing application are analyzed and a framework for structured P2P overlay over delay tolerant disconnected MANETs is proposed. The framework is implemented and tested on J2ME based smart phones using Bluetooth communication protocol. A light weight Content Driven Data Propagation Protocol (CDDPP) for content based data delivery in MANETs is presented. The CDDPP implements a user profile based content driven P2P file sharing application in disconnected MANETs. The CDDPP protocol is further enhanced by proposing an adaptive opportunistic multihop content based routing protocol (ORP). ORP protocol considers the store-carry-forward paradigm for multi-hop packet delivery in delay tolerant MANETs and allows multi-casting to selected number of nodes. Performance of ORP is compared with a similar autonomous gossiping (A/G) protocol using simulations. This work also presents a framework for trust management based on dynamicity aware graph re-labelling system (DA-GRS) for trust management in mobile P2P applications. The DA-GRS uses a distributed algorithm to identify trustworthy nodes and generate trustable groups while isolating misleading or untrustworthy nodes. Several simulations in various environment settings show the effectiveness of the proposed framework in creating trust based communities. This work also extends the FIRE distributed trust model for MANET applications by incorporating witness based interactions for acquiring trust ratings. A witness graph building mechanism in FIRE+ is provided with several trust building policies to identify malicious nodes and detect collusive behaviour in nodes. This technique not only allows trust computation based on witness trust ratings but also provides protection against a collusion attack. Finally, M-trust, a light weight trust management scheme based on FIRE+ trust model is presented.

The aim of this study was to investigate the various reasons consumers continue to infringe on copyrighted content, specifically in the South African context, even if the law forbids it. This investigation is two-fold since it also recognises that there are many individuals who do not infringe on copyrighted content even though they have access to peer-to-peer file sharing technology. This information could prove valuable since it can then be used to find comprehensive market-led solutions to the problem that targets the end-user. This study adopted a mixed method approach in order to cross validate findings and to reveal aspects of empirical reality. The target population for this study consisted of 100 adult South Africans who have access to the internet. Data was collected through an online, self-administered questionnaire. Quantitative data was analysed through descriptive statistics, while qualitative data was analysed through thematic analysis. The results show that there are variety of factors that influence respondents’ attitudes towards copyright infringement of films and/or television series through peer-to-peer file sharing technology, each of which is discussed in detail. The study concluded by identifying 24 factors that favourably influence people’s attitudes towards copyright infringement, including high prices of legitimate goods, historical inequality in South Africa, and perceived low risk of being caught and punished. Based on the conclusion above, the study recommends that policy makers such as government officials, boards of directors, managers, committees, and executives use the results of the study when making decisions and determining policies, especially in the South African context. / Communication Science / M.A. (Communication Science)

A study is done on the protection of sound recordings in the decentralized peer-to-peer (DP2P) file sharing in the United States, the United Kingdom and South Africa. This study reveals that because sound recordings have unique features different from other copyright works, the illegal sharing of sound recordings can ordinarily be filtered, identified, and detected by the Internet service providers (ISPs) before granting access to users and without infringing the users‟ right to privacy. However, the ISPs have failed in this regard, hence, they are strictly held liable under the contributory, vicarious and inducing infringements notwithstanding the statutory law which prohibits ISPs from monitoring, and intercepting their networks. In fact and law, the terms filtering, identifying and detecting on the one hand and monitoring and intercepting on the other hand are different in relation to sound recordings and as such ISPs are not prohibited from filtering, identifying and detecting illegal sound recordings on their networks, thus, ISPs are not protected under the limitation law as it is generally believed. However, several recommendations are made for reform, inter alia: a review of the limitation law to include the terms filtering, identifying and detecting in pursuance of the terms monitoring, and intercepting, if the intention of the legislators was meant to include the latter terms; protection of access right in digital sound recordings, protection of the neighbouring rights of ISPs in the digital world, imposing levies on all recording equipment, the insurability of sound recordings and ISPs‟ signals, and bandwidth. / Mercentile Law / LL. M. (Mercantile Law)

A study is done on the protection of sound recordings in the decentralized peer-to-peer (DP2P) file sharing in the United States, the United Kingdom and South Africa. This study reveals that because sound recordings have unique features different from other copyright works, the illegal sharing of sound recordings can ordinarily be filtered, identified, and detected by the Internet service providers (ISPs) before granting access to users and without infringing the users‟ right to privacy. However, the ISPs have failed in this regard, hence, they are strictly held liable under the contributory, vicarious and inducing infringements notwithstanding the statutory law which prohibits ISPs from monitoring, and intercepting their networks. In fact and law, the terms filtering, identifying and detecting on the one hand and monitoring and intercepting on the other hand are different in relation to sound recordings and as such ISPs are not prohibited from filtering, identifying and detecting illegal sound recordings on their networks, thus, ISPs are not protected under the limitation law as it is generally believed. However, several recommendations are made for reform, inter alia: a review of the limitation law to include the terms filtering, identifying and detecting in pursuance of the terms monitoring, and intercepting, if the intention of the legislators was meant to include the latter terms; protection of access right in digital sound recordings, protection of the neighbouring rights of ISPs in the digital world, imposing levies on all recording equipment, the insurability of sound recordings and ISPs‟ signals, and bandwidth. / Mercentile Law / LL. M. (Mercantile Law)

Peer-to-Peer(P2P)架構讓社群內的使用者收集分散在網路各處之資源，其中最為風行的P2P系統當屬P2P檔案分享系統。P2P檔案分享系統之架構可分為集中式及分散式，而分散式架構又可細分為結構化及非結構化兩種。採用分散式且非結構化之BitTorrent-like架構，因其可擴張性較佳而廣為風行。在經驗中發現，BitTorrent-like架構在非對稱網路之下雖擁有寬裕的下行頻寬，但是其頻寬使用率卻不高，我們分析其成因如下：(1) Fractional Upward Bandwidth (FUB) 、 (2)Blockage of Acknowledgement (BoA) 與 (3)Long Physical Paths 等。而其中的Blockage of ACK問題，現今尚未有研究學者提出完整解決方案。本研究之目的，即要針對此Blockage of ACK的問題，改良網路協定中的傳輸層 (Transport Layer) 協定以提昇P2P檔案分享系統之效能。我們改用UDP作為傳輸層協定，並在應用層加入自動重建遺失之封包、決定基本傳輸單位大小及決定資料傳送速率等機制，以彌補UDP之缺陷。文中並提供了傳輸協定運作時所需參數的估計法，並且也與其它傳輸協定做效能之比較。實驗結果發現，我們設計的傳輸協定確可改善P2P檔案共享系統的運作效能。 / Peer-to-Peer (P2P) architectures let participants gather resources form network and make participants acquire more computation resources than they could offer. One of the most prominent P2P systems is P2P file sharing system. P2P file sharing system could be classified into to 2 categories: centralized and decentralized model. BitTorrent-like (BT-like) model can be classified as decentralized and unstructured model. BT-like model is quit popular nowadays due to its scalability. Unfortunately, BT-like model has several shortcomings on performance over asymmetric networks, because of some problems, such as Fractional Upward Bandwidth (FUB), Blockage of Acknowledgement (BoA) and long physical paths. No complete solution is available yet to solve the BoA problem. We propose a new UDP-based protocol to alleviate this problem. Since UDP protocol is not able to guarantee the data-integrity nor to determine the proper transmission rate by itself. To offer a complete solution, we have to enhance UDP, to add extra capabilities such as packet loss recovery, segment size determination and data rate determination mechanisms. Experiments show that our proposed protocol has good improvement on performance.

"Traditional security models are out of place in peer networks, where no hierarchy ex- ists, and where no outside channel can be relied upon. In this nontraditional environment we must provide traditional security properties and assure fairness in order to enable the secure, collaborative success of the network. One solution is to form a Trusted Domain, and exclude perceived dishonest and unfair members. Previous solutions have been intolerant of masquerading, and have suffered from a lack of precise control over the allocation and exercise of privileges within the Trusted Domain. Our contribution is the introduction of a model that allows for controlled access to the group, granular control over privileges, and guards against masquerading. Contin- ued good behavior is rewarded by an escalation of privileges, while requiring an increased commitment of resources. Bad behavior results in expulsion from the Trusted Domain. In colluding with malicious nodes, well behaved nodes risk losing privileges gained over time; collusion is thereby discouraged. We implement our solution on top of the Bouncer Toolkit, produced by Narasimha et al. [7], as a prototype peer to peer network. We make use of social models for trust from [], and rely on new cryptographic primitives from the field of Threshold Cryptography. We present the results of an experimental analysis of its performance for a number of thresholds, and present observations on a number of important performance and security improvements that can be made to the underlying toolkit."

Submitted by Mariana Dornelles Vargas (marianadv) on 2015-03-24T14:39:54Z No. of bitstreams: 1 lp2p.pdf: 907325 bytes, checksum: f14a60879bfa80f3f2b600d16e6b6d0f (MD5) / Made available in DSpace on 2015-03-24T14:39:54Z (GMT). No. of bitstreams: 1 lp2p.pdf: 907325 bytes, checksum: f14a60879bfa80f3f2b600d16e6b6d0f (MD5) Previous issue date: 2011-03-30 / Nenhuma / Nos últimos anos, o crescimento da Internet e o surgimento de novos serviços em rede contribuíram para o desenvolvimento de várias arquiteturas destinadas à computação distribuída. Neste contexto, a tecnologia P2P tem fomentado o interesse da comunidade científica em decorrência de suas características e funcionalidades inovadoras. Um dos fatores responsáveis por esta popularidade é proveniente das aplicações destinadas ao compartilhamento de arquivos. Este serviço também ocorre de forma expressiva em redes de menor abrangência (ex. LANs), onde recursos presentes nas estações de trabalho são muitas vezes desperdiçados enquanto as corporações investem maciçamente em infraestrutura específica para prover este serviço. Uma possível alternativa frente a este cenário, está na adaptação de alguns conceitos do paradigma P2P à infraestrutura de rede local. No entanto, há poucos esforços no sentido de explorar o potencial da comunicação peer-to-peer aliada aos padrões e vantagens disponíveis nas LANs. Em virtude de sua natureza distribuída, as abordagens P2P convencionais adotam este sistema principalmente em redes de longa distância (MANs e WANs) para formação da estrutura overlay. Contudo, estes aspectos não inviabilizam a utilização de algumas técnicas e características da tecnologia P2P em redes de menor abrangência. Este conjunto de fatores motivaram a proposta do LP2P-Local Peer-to-Peer-Protocol-, uma plataforma de comunicação distribuída e descentralizada que aplica a tecnologia P2P no compartilhamento de arquivos em redes locais. / In recent years, the growth of the Internet and the emergence of new network services contributed to the development of various architectures for distributed computing. In this context, P2P technology has fostered the interest of the scientific community due to its features and innovative characteristies. One of the factors responsible for this popularity is coming from consumer applications and file sharing. This service also occurs in a significant way into networks of smaller scope (e.g. LANs), where features present in the workstations are often wasted while corporations invest heavily in infrastructure to provide this particular service. A possible alternative in the face of this scenario is the adaptation of some concepts of P2P paradigm to the local network infrastructure. However, there are few efforts to explore the potential of communication peer-to-peer coupled with the patterns and advantages available in LANs. Due to its distributed nature, conventional P2P approaches adopted this system mainly in long distance (MANs and WANs) to overlay structure formation. However, these aspects do not make use of some techniques and features of P2P networks smaller. These factors motivated the proposal of LP2P-Local Peer-to-Peer-Protocol- a distributed communications platform that applies technology in P2P file sharing on local networks.

Record companies are suffering due to a downturn in recorded music sales. Innovative firms have developed digital music services that offer recorded music products to customers in new ways, yet sales are not what they used to be. Web 2.0 technologies have changed the customer’s tastes, expectations, and desires. Thus, a deeper understanding of the new “digital customer” is needed in order to better offer services in a way that he or she prefers most.

Most current-generation P2P content distribution protocols use fine-granularity blocks to distribute content in a decentralized fashion. Such systems often suffer from a significant variation in block distributions, such that certain blocks become rare or even unavailable, adversely affecting content availability and download efficiency. This phenomenon is further aggravated by peer dynamics which is inherent in P2P networks. In this thesis, we quantitatively analyze how network coding may improve block availability and introduce resilience to peer dynamics. Since in reality, network coding can only be performed within segments, each containing a subset of blocks, we explore the fundamental tradeoff between the resilience gain of network coding and its inherent coding complexity, as the number of blocks in a segment varies. As another application of the resilience of network coding, we also devise an indirect data collection scheme based on network coding for the purpose of large-scale network measurements.

Most current-generation P2P content distribution protocols use fine-granularity blocks to distribute content in a decentralized fashion. Such systems often suffer from a significant variation in block distributions, such that certain blocks become rare or even unavailable, adversely affecting content availability and download efficiency. This phenomenon is further aggravated by peer dynamics which is inherent in P2P networks. In this thesis, we quantitatively analyze how network coding may improve block availability and introduce resilience to peer dynamics. Since in reality, network coding can only be performed within segments, each containing a subset of blocks, we explore the fundamental tradeoff between the resilience gain of network coding and its inherent coding complexity, as the number of blocks in a segment varies. As another application of the resilience of network coding, we also devise an indirect data collection scheme based on network coding for the purpose of large-scale network measurements.