<p>Innehåll: Peer-to-peer är idag en teknik som i de flesta fall förknippas med fildelning.</p><p>I detta arbete har vi försökt klargöra vilka andra möjligheter tekniken erbjuder för företag och i dessa möjligheter försökt hitta fördelar och nackdelar med tekniken. Klient-server är en vanlig teknik idag bland företag och i arbetet undersöks om peer-to-peer kan vara en möjlig konkurrent till denna teknik.</p><p>Syftet med rapporten är att se om det finns intresse bland företagen att använda sig av de möjligheter som peer-to-peer tekniken erbjuder samt att undersöka hur den skulle kunna användas.</p> / <p>Contents: Peer-to-peer is a technique that is most often associated with file sharing. In this thesis we try to examine what other possibilities the technique has to offer to companies, and in these possibilities, determine pros and cons. Client-server is a common technique today, especially amongst companies, and in this thesis we study if peer-to-peer can be a possible competitor to this technique. The purpose with the study is to see if companies are interested in using the possibilities offered in the peer-to-peer technique and how these possibilities could be used in a company.</p>

Millions of users world-wide are sharing content using Peer-to-Peer (P2P) networks, such as Skype and Bit Torrent. While such new innovations undoubtedly bring benefits, there are nevertheless some associated threats. One of the main hazards is that P2P worms can penetrate the network, even from a single node and then spread rapidly. Understanding the propagation process of such worms has always been a challenge for researchers. Different techniques, such as simulations and analytical models, have been adopted in the literature. While simulations provide results for specific input parameter values, analytical models are rather more general and potentially cover the whole spectrum of given parameter values. Many attempts have been made to model the worm propagation process in P2P networks. However, the reported analytical models to-date have failed to cover the whole spectrum of all relevant parameters and have therefore resulted in high false-positives. This consequently affects the immunization and mitigation strategies that are adopted to cope with an outbreak of worms. The first key contribution of this thesis is the development of a susceptible, exposed, infectious, and Recovered (SEIR) analytical model for the worm propagation process in a P2P network, taking into account different factors such as the configuration diversity of nodes, user behaviour and the infection time-lag. These factors have not been considered in an integrated form previously and have been either ignored or partially addressed in state-of-the-art analytical models. Our proposed SEIR analytical model holistically integrates, for the first time, these key factors in order to capture a more realistic representation of the whole worm propagation process. The second key contribution is the extension of the proposed SEIR model to the mobile M-SEIR model by investigating and incorporating the role of node mobility, the size of the worm and the bandwidth of wireless links in the worm propagation process in mobile P2P networks. The model was designed to be flexible and applicable to both wired and wireless nodes. The third contribution is the exploitation of a promising modelling paradigm, Agent-based Modelling (ABM), in the P2P worm modelling context. Specifically, to exploit the synergies between ABM and P2P, an integrated ABM-Based worm propagation model has been built and trialled in this research for the first time. The introduced model combines the implementation of common, complex P2P protocols, such as Gnutella and GIA, along with the aforementioned analytical models. Moreover, a comparative evaluation between ABM and conventional modelling tools has been carried out, to demonstrate the key benefits of ease of real-time analysis and visualisation. As a fourth contribution, the research was further extended by utilizing the proposed SEIR model to examine and evaluate a real-world data set on one of the most recent worms, namely, the Conficker worm. Verification of the model was achieved using ABM and conventional tools and by then comparing the results on the same data set with those derived from developed benchmark models. Finally, the research concludes that the worm propagation process is to a great extent affected by different factors such as configuration diversity, user-behaviour, the infection time lag and the mobility of nodes. It was found that the infection propagation values derived from state-of-the-art mathematical models are hypothetical and do not actually reflect real-world values. In summary, our comparative research study has shown that infection propagation can be reduced due to the natural immunity against worms that can be provided by a holistic exploitation of the range of factors proposed in this work.

I princip hela IT-världen ser på och häpnar medan Blockchain-tekniken växer. Många spekulerar om fördelar och nackdelar med tekniken. Men hur ser egentligen samhället på detta nya sättet att lagra data på? Det finns väldigt lite forskning på hur Blockchain uppfattas i Sverige, hur tekniken uppfattas och vad folk vet om tekniken. Det har inte heller hittats någon undersökning som tar upp graden av tillit privatpersoner har till Blockchain i Sverige och vad för faktorer det är som påverkar privatpersoners tillit. För att tekniken ska kunna accepteras på en större skala behöver man veta vad privatpersoner och konsumenter tycker om tekniken, annars finns det risk att tekniken inte omfamnas i framtiden. Syftet med denna undersökningen är att, på ett explorativt sätt, ta reda på till vilken grad privatpersoner i Sverige har tillit för Blockchain som teknik. Undersökningen skall också, i ett explorativt syfte, identifiera faktorer till varför den svenska befolkningen litar mer eller mindre på Blockchain. Studien använder sig av både kvalitativa och kvantitativa datainsamlingstekniker. Det utfördes en kvalitativ studie i form av personliga intervjuer för att ta reda på vad privatpersoner vet om Blockchain, och vad folk anser är viktiga faktorer som påverkar deras tillit för tekniken. Den kvalitativa undersökningen utfördes för att säkra att den sedan kvantitativa undersökningen fick in så pålitlig data som möjligt. Den kvantitativa undersökningen var en enkätstudie. I enkäten var det frågor som behandlade tillit, kunskap om ämnet, generell inställning till ny teknik och bakgrundsfrågor om respondenten. I analysen har det framgått att 10,47% privatpersoner från undersökningen i Västra Götalands län litar mindre på Blockchain, 19,19% litar inte alls på tekniken, 63,95% litar neutralt på den, 4,1% litar ganska mycket på den och 2,33% litar fullt ut på den. Utifrån detta kan slutsatsen dras att tillitsgraden är relativt låg. Resultatet visade också att det fanns ett antal återkommande faktorer som påverkade privatpersoners tillit för Blockchain. Dessa faktorer var manipulering, decentralisering och att Blockchain anses vara relaterat till svarta marknaden. Vidare kan man utifrån denna undersökning utläsa både en låg kunskapsnivå samt en hög neutral attityd till tekniken. Detta skulle kunna anses som någonting positivt för teknikens framtid då få förutfattade meningar finns. Mer information om Blockchain skulle därmed kunna vara en möjlighet för ökad tillit. För vidare forskning föreslogs det att det bör forskas mer om detta utanför Västra Götalands län och att man bör undersöka om privatpersoner kan tänka sig använda tekniken även om de inte litar på tekniken fullt ut. / Developments in Blockchain technology has grown so rapidly that it has, in a short time, become a core business in the IT industry. These developments have come with positive and negative impacts and their overall perception by society has remained uncertain. Limited work has focused on understanding the societal perception of Blockchain, particularly the extent to which society trust such technology. Moreover, it is not only important to understand the level of trust for a technology such as Blockchain that is built on transparency, but even the factors that influence such trust. In order for the technology to be accepted on a larger scale, one needs to know what individuals and consumers think about the technology, otherwise there is a risk that that the potential of the technology may not be fully utilized. The purpose of this study is, therefore, to explore the extent to which individuals in Sweden trust Blockchain as a technology. The overall goals and approach can be applied anywhere else in the world. The report identifies factors as to why the Swedish population trusts more or less in Blockchain. The study uses both qualitative and quantitative data collection techniques. A qualitative study was conducted in the form of personal interviews to find out what individuals know about Blockchain, and what people consider to be important factors that affect their trust in Blockchain. The qualitative survey was conducted to build a foundation for the quantitative study. The quantitative survey was conducted with the help of questionnaires. The questionnaire addressed trust, knowledge of the technology, as well as respondent's general attitude toward new technology. The respondents were restricted to a sample of individuals living in Sweden between age range 18 to 65+. Based on the survey sample of about 172 participants, the analysis shows that 10.47% of individuals in the Västra Götaland county are less familiar with Blockchain, 19.19% do not count on the technology at all, 63.95% are neutral, 4.1% trust it fairly and 2.33% fully trust it. From this, the conclusion can be drawn that the trust is relatively low. The result also showed that there were a number of recurring factors that affected individuals' confidence in Blockchain. These factors were data integrity, decentralization and the fact that Blockchain is considered to be related to the black market. Furthermore, on the basis of this survey, it is possible to interpret both a low level of knowledge and a high neutral attitude towards the technology. This could be considered as something positive for the future of technology as few pre-defined opinions exist. More information about Blockchain could thus be an opportunity for increased trust. For further research, it was suggested that more research should be done involving a much larger sample in order to investigate if individuals would be willing to accept the technology even if they do not fully trust the technology.

Made available in DSpace on 2014-12-17T14:55:45Z (GMT). No. of bitstreams: 1 FranciscoSLF_DISSERT.pdf: 3096340 bytes, checksum: fbb14f36dfa3f807cc960ba2d74b9f0a (MD5) Previous issue date: 2010-11-03 / Previous works have studied the characteristics and peculiarities of P2P networks, especially security information aspects. Most works, in some way, deal with the sharing of resources and, in particular, the storage of files. This work complements previous studies and adds new definitions relating to this kind of systems. A system for safe storage of files (SAS-P2P) was specified and built, based on P2P technology, using the JXTA platform. This system uses standard X.509 and PKCS # 12 digital certificates, issued and managed by a public key infrastructure, which was also specified and developed based on P2P technology (PKIX-P2P). The information is stored in a special file with XML format which is especially prepared, facilitating handling and interoperability among applications. The intention of developing the SAS-P2P system was to offer a complementary service for Giga Natal network users, through which the participants in this network can collaboratively build a shared storage area, with important security features such as availability, confidentiality, authenticity and fault tolerance. Besides the specification, development of prototypes and testing of the SAS-P2P system, tests of the PKIX-P2P Manager module were also performed, in order to determine its fault tolerance and the effective calculation of the reputation of the certifying authorities participating in the system / Trabalhos anteriores estudaram caracter?sticas e peculiaridades das redes P2P, especialmente no que se refere aos aspectos de seguran?a da informa??o. A maioria dos trabalhos aborda, de alguma maneira, o compartilhamento de recursos e, em especial, o armazenamento de arquivos. Este trabalho complementa estudos anteriores e acrescenta novas defini??es referentes a este tipo de sistemas. Foi especificado e constru?do um sistema de armazenamento seguro baseado na tecnologia P2P (SAS-P2P), utilizando a plataforma JXTA. Tal sistema utiliza certificados digitais padr?o X.509 e PKCS#12 (RSA 1999), emitidos e gerenciados por uma infraestrutura de chaves p?blicas, que tamb?m foi especificada e constru?da baseada na tecnologia P2P (PKIX-P2P). As informa??es s?o armazenadas no sistema SAS-P2P em arquivos no formato XML que ? especialmente preparado, facilitando a manipula??o e interoperabilidade entre aplica??es. O sistema SAS-P2P foi desenvolvido com o intuito de ser oferecido como um servi?o complementar da rede GigaNatal, atrav?s do qual os participantes dessa rede possam, colaborativamente, construir uma ?rea de armazenamento compartilhada com importantes recursos de seguran?a como disponibilidade, confidencialidade, autenticidade e toler?ncia a falhas. Al?m da especifica??o, constru??o e experimentos do sistema SAS-P2P como um todo, tamb?m foram realizados testes do m?dulo PKIX-P2P no que se refere ? toler?ncia a falhas e c?lculo efetivo da reputa??o das autoridades certificadoras participantes do sistema

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Peer-to-peer networks provide an efficient way for sharing computer resources. The transport layer underlies these networks. On the Internet, TCP and UDP are the mostly used protocols in this layer. SCTP is another transport layer protocol: related to TCP and UDP, SCTP offers additional functionalities that makes it more suitable to certain kinds of applications. This work aims to show the viability of the use of SCTP as the transport layer protocol for peer-to-peer file sharing applications, using the peculiar functionalities of this protocol to satisfy the needs of these applications in a more efficient way. / As redes peer-to-peer oferecem uma forma eficaz para o compartilhamento de recursos dos computadores. Sob essas redes está a camada de transporte. Na Internet, os protocolos mais utilizados nessa camada são o TCP e o UDP. Outro protocolo da camada de transporte e o SCTP, que oferece funcionalidades adicionais em relação ao TCP e ao UDP que o tornam mais apropriado a determinados tipos de aplicações. Este trabalho tem como objetivo mostrar a viabilidade da utiliza¸são do SCTP como protocolo da camada de transporte em aplicativos peer-to-peer de compartilhamento de arquivos, fazendo uso das funcionalidades peculiares a esse protocolo para satisfazer de forma mais eficaz as necessidades destes aplicativos. / Mestre em Ciência da Computação

Orientador: Paulo Licio de Geus / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-13T11:26:28Z (GMT). No. of bitstreams: 1 Quinellato_DouglasGielo_M.pdf: 2170090 bytes, checksum: 70af102166738a9e7bd99af678848faf (MD5) Previous issue date: 2009 / Resumo: As redes P2P ganharam bastante popularidade na ultima decada, consolidando-se como um dos serviços mais populares da internet, provendo uma arquitetura distribuída para o fornecimento de servi¸cos sem a necessidade de um host assumir o papel de servidor. A popularidade trouxe, entretanto, a necessidade de se desenvolver mecanismos para garantir o funcionamento perante os crescentes ataques 'a rede. Com a estabilidade dos algoritmos relacionados ao funcionamento das redes P2P foi possível um aumento no desenvolvimento destes mecanismos de segurança. Nesta dissertação e proposto um sistema de reputação para redes P2P de compartilhamento de arquivos, um mecanismo de seguran¸ca que visa impedir a proliferação de arquivos corrompidos. Tais sistemas funcionam gerenciando as opiniões emitidas pelos nós participantes da rede sobre os serviços prestados pelos outros nós. Estas opiniões podem ser sobre o nó que prestou o serviço ou sobre a qualidade do serviço prestado. As opiniões sobre um mesmo nó ou serviço avaliado são armazenadas e posteriormente agregadas atraves de uma função, formando a reputação destes. O mecanismo proposto baseia-se nas opiniões emitidas sobre a autenticidade os arquivos, utilizando a reputação dos nós para indicar a qualidade da opinião sendo emitida por eles. Essa verificação da qualidade da opinião visa aumentar a confiança na opinião utilizada com a adicão de um nível de verificação por motivos de eficiência, visto que implementar uma rede de confiança inteira é custosa. Foram realizadas simulaçõs para a verificação da eficácia da rede, realizando comparações tanto com uma rede sem nenhum sistema de reputação quanto com outros sistemas de reputação. / Abstract: P2P networks have earned a great deal of popularity over the last decade, consolidating itself as one of the most popular internet service, providing a distributed architecture for the furnishing of services without the need of a centralized server host. However, such popularity brought the necessity for security mechanisms in order to assure the network availability in spite of the attacks on the network. Stability in the algorithms related to the basic operation of the P2P networks made possible the rise on the development of security systems. In this dissertation it's proposed a reputation system for file sharing P2P networks, a security mechanism aimed at lowering the spread of corrupted files in the network. Such systems work by managing the opinions issued by the participants of the network about the received services from the other nodes. These opinions can be about the nodes, or about the quality of the services themselves. Opinions about the same service or node are them joined through the use of a mathematical model (function), calculating their reputation. The proposed reputation system is based on the reputation of the files, using the node reputation as a means to assess the quality of the opinion being issued. This check is made with the purpose of improving trust in the used opinion by adding one level of opinion checking. Only one level is used for efficiency, since implementing a full trust network is expensive. Simulations were used in order to assess the effectiveness of the proposed reputation system. The results are used in comparisons with the same simulation without the use of any reputation system, and with the results of other reputation systems found in the literature. / Mestrado / Segurança de Redes / Mestre em Ciência da Computação

Orientador: Edmundo Roberto Mauro Madeira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-11T15:56:37Z (GMT). No. of bitstreams: 1 Siqueira_ThiagoSenadorde_M.pdf: 7328903 bytes, checksum: f944c1a0baac79f360047d39c4871f32 (MD5) Previous issue date: 2008 / Resumo: A computação sobre P2P tem surgido como uma solução alternativa e complementaràs grades computacionais. O uso da tecnologia P2P é capaz de prover a flexibilização e descentralização dos processos de execução e gerenciamento de workflows nas grades computacionais. Neste trabalho é apresentado um middleware P2P completamente descentralizado para a computação de workflows. O middleware coleta o poder de processamento compartilhado pelos peers para possibilitar a execução de workflows, modelados como DAGs, compostos por um conjunto de tarefas dependentes. Através do processo distribuído de escalonamento de tarefas e do mecanismo de tolerância a faltas baseado em leasing, o middleware atinge um nível alto de paralelismo na execução e eficiência na recuperação de execuções em ocorrência de faltas. O middleware é implementado em Java, juntamente com RMI e a biblioteca JXTA. Os resultados experimentais obtidos mostram a eficiência do middleware na execução distribuída dos workflows assim como a recuperação rápida de execução em cenários com faltas / Abstract: P2P Computing has been raised as an alternative and complementary solution to Grid Computing. The use of P2P technology is able to provide a flexible and decentralized execution and management of Grid workflows. In this work we present a completely decentralized P2P middleware for workflow computing. The middleware collects the shared processing power of the peers in order to execute workflows, modeled as DAG structures, composed of a set of dependent tasks. Through a distributed scheduling algorithm and a leasing-based fault tolerance mechanism, the middleware achieves high execution parallelism and efficient execution recovery in failure occurrences. The middleware is implemented in Java, through RMI and the JXTA library. The obtained experimental results show the efficiency of the middleware in the distributed execution of workflows as well as the fast execution recovery / Mestrado / Ciência da Computação / Mestre em Ciência da Computação

Made available in DSpace on 2016-08-17T14:53:02Z (GMT). No. of bitstreams: 1 Flavio_Marcilio_Paiva_Ramos.pdf: 2116529 bytes, checksum: ec39ed91f835e580a43ccfbf8a3c4d1a (MD5) Previous issue date: 2009-05-04 / Nowadays, peer-to-peer networks are very popular mainly, when we wish to search or share a considerable amount of information and resources among various participants. One of the main difficulties of this technology is how to avoid that those participants maintain, at the same time, a considerable number of shared resources and to guarantee that those resources are not corrupted or polluted content. Another problem commonly found in P2P networks is the lack of interoperability among existing P2P solutions especially because the inconsistencies of metadata and operation interfaces used in node communication. This work describes P2PWSRep, a reputation management protocol that identifies non-cooperative nodes or that can hinder network performance by sharing corrupted, infected or non-existent files. P2PWSRep infrastructure was based on web services in order to tackle interoperability problems and to facilitate its extensibility, making it feasible to be accessed by several other P2P applications. The P2PWSRep protocol employs a distributed reputation computation using an exponentially weighted average that takes into account the current and previous node reputation and which is tuned by an adjustment parameter in order to obtain the final reputation, thus considering the node s behavior. The P2PWSRep protocol is validated by means of simulation and our results show that it is able to point out the more trustable nodes in the network as well as to insulate those which are not reliable or cooperative. Besides, the protocol does not unnecessarily impacts on the network load P2PWS. / As redes peer-to-peer (P2P) são muito populares atualmente, principalmente quando se deseja buscar ou compartilhar uma grande quantidade de informações e recursos entre os seus participantes. Uma das grandes dificuldades desse tipo de tecnologia é evitar que esses participantes mantenham, ao mesmo tempo, um número considerável de arquivos compartilhados, e ainda garantir que esses arquivos não sejam conteúdo poluído ou corrompido. Outro problema bem comum nas redes P2P, é a falta de interoperabilidade entre as diversas redes existentes, principalmente devido às incompatibilidades dos metadados e das interfaces das operações utilizadas na comunicação entre os nós. Este trabalho descreve o P2PWSRep, um protocolo de gerenciamento de reputação para identificar nós que não desejam cooperar ou que podem prejudicar o desempenho da rede pelo compartilhamento de arquivos corrompidos, infectados ou inexistentes. A infraestrutura da rede do P2PWSRep foi baseada em serviços web para contornar problemas de interoperabilidade e facilitar sua extensibilidade, tornando-o fácil de ser utilizado por diversas aplicações de redes P2P. O protocolo P2PWSRep possui um cállculo de reputação distribuído, utilizando-se uma média ponderada exponencial, que considera o valor da reputação anterior do nó e o valor atual, obtido dos demais nós da rede, e regulado por um parâmetro de ajuste, para obter a reputação final, de forma que o histórico do comportamento do nó seja considerado. O protocolo P2PWSRep é validado por meio de simulação e os resultados obtidos mostram que o mesmo é capaz de apontar os nós ou recursos mais confiáveis da rede, ao mesmo tempo em que isola aqueles nós que não são íntegros ou pouco cooperativos, além de não impor uma sobrecarga desnecessária à rede P2PWS.

Innehåll: Peer-to-peer är idag en teknik som i de flesta fall förknippas med fildelning. I detta arbete har vi försökt klargöra vilka andra möjligheter tekniken erbjuder för företag och i dessa möjligheter försökt hitta fördelar och nackdelar med tekniken. Klient-server är en vanlig teknik idag bland företag och i arbetet undersöks om peer-to-peer kan vara en möjlig konkurrent till denna teknik. Syftet med rapporten är att se om det finns intresse bland företagen att använda sig av de möjligheter som peer-to-peer tekniken erbjuder samt att undersöka hur den skulle kunna användas. / Contents: Peer-to-peer is a technique that is most often associated with file sharing. In this thesis we try to examine what other possibilities the technique has to offer to companies, and in these possibilities, determine pros and cons. Client-server is a common technique today, especially amongst companies, and in this thesis we study if peer-to-peer can be a possible competitor to this technique. The purpose with the study is to see if companies are interested in using the possibilities offered in the peer-to-peer technique and how these possibilities could be used in a company.

The wide-spread coverage and ubiquitous presence of mobile networks has propelled the usage and adoption of mobile phones to an unprecedented level around the globe. The computing capabilities of these mobile phones have improved considerably, supporting a vast range of third party applications. Simultaneously, Peer-to-Peer (P2P) overlay networks have experienced a tremendous growth in terms of usage as well as popularity in recent years particularly in fixed wired networks. In particular, Distributed Hash Table (DHT) based Structured P2P overlay networks offer major advantages to users of mobile devices and networks such as scalable, fault tolerant and self-managing infrastructure which does not exhibit single points of failure. Integrating P2P overlays on the mobile network seems a logical progression; considering the popularities of both technologies. However, it imposes several challenges that need to be handled, such as the limited hardware capabilities of mobile phones and churn (i.e. the frequent join and leave of nodes within a network) intensive mobile networks offering limited yet expensive bandwidth availability. This thesis investigates the feasibility of extending P2P to mobile networks so that users can take advantage of both these technologies: P2P and mobile networks. This thesis utilises OverSim, a P2P simulator, to experiment with the performance of various P2P overlays, considering high churn and bandwidth consumption which are the two most crucial constraints of mobile networks. The experiment results show that Kademlia and EpiChord are the two most appropriate P2P overlays that could be implemented in mobile networks. Furthermore, Network Address Translation (NAT) is a major barrier to the adoption of P2P overlays in mobile networks. Integrating NAT traversal approaches with P2P overlays is a crucial step for P2P overlays to operate successfully on mobile networks. This thesis presents a general approach of NAT traversal for ring based overlays without the use of a single dedicated server which is then implemented in OverSim. Several experiments have been performed under NATs to determine the suitability of the chosen P2P overlays under NATed environments. The results show that the performance of these overlays is comparable in terms of successful lookups in both NATed and non-NATed environments; with Kademlia and EpiChord exhibiting the best performance. The presence of NATs and also the level of churn in a network influence the routing techniques used in P2P overlays. Recursive routing is more resilient to IP connectivity restrictions posed by NATs but not very robust in high churn environments, whereas iterative routing is more suitable to high churn networks, but difficult to use in NATed environments. Kademlia supports both these routing schemes whereas EpiChord only supports the iterating routing. This undermines the usefulness of EpiChord in NATed environments. In order to harness the advantages of both routing schemes, this thesis presents an adaptive routing scheme, called Churn Aware Routing Protocol (ChARP), combining recursive and iterative lookups where nodes can switch between recursive and iterative routing depending on their lifetimes. The proposed approach has been implemented in OverSim and several experiments have been carried out. The experiment results indicate an improved performance which in turn validates the applicability and suitability of ChARP in NATed environments.