Nowadays, we can get the wireless devices easily, such as cell phone, PDA, etc. It can make the life convenient. The P2P network which has been constructed by the wireless devices does not need the central server. They can communicate by themselves. Not only have protected in the privacy, but also add the convenience. The reason is that the devices are portable, we can get the newest information. Some P2P software focuses on the sharing. They can share files with other peer. The file can separate into several modes. The software will share these nodes. Every peer shares his own node, and it will speed up the rate of sharing. There are some selfish peers in this environment, and they will not want to share their own node. Moreover, some of them share the incorrect file. The software will solve this kind of problem by some mechanism. And it set some incentive mechanism to make the sharing to go on. Because the wireless devices are portable, we can use these devices for exchanging immediate information. Sharing the files is similar to the exchanging. Both of the users trust each other. They can exchange automatically. So, our research has designed a reputation based mechanism for exchanging. The users can evaluate each other to exchanging the information automatically. By this mechanism, the user in our system will exchange continuously. We can reach our purpose which makes the user in our environment can exchange automatically.

As the global wireless network becoming mature, the growing number of mobile devices, and the personal need of keeping in touch with others daily, mobile communication is becoming a necessity of life. Using mobile devices, such as cell phones or PDAs, everyone could communicate with each other independently; and this communication environment is similar with P2P network. Utilizing the connection network of cell phones is becoming a brand new business channel. Since group-buying is part of our daily life, people live in the same area could buy products or services together based on mutual needs, and this could enhance the bargaining power of customers and lower the purchase price. This research proposes a group-buying system architecture under mobile environment, and discusses the problems that customers might encounter in every stage of the buying process. Mobile device users under the environment could exchange information with each other and this could help customers search group-buying information efficiently. Sensor Network combines with MP2P Network accelerates the spread of group-buying information in a marketplace, and helps the originator and other buyers to negotiate with the supplier. Based on the observation of the variation of the group-buying information distribution in the experiment, we summarize under what situation a better information distribution would take place in a specific marketplace.

The goodness of group buying is consumers can buy product with lower price, and seller can reduce the bargain cost by collecting orders. But it is hard to be realized in the mall. A recent survey shows most everyone has his own mobile device. In this research, we organize a mobile P2P network by exchanging between two mobile devices. We propose a system for consumers and sellers to exchange group buying information. In Mobile P2P Network environment, group buying initiator is hard to decide the best timing to end the group buying. Because buyers can easily participate or leave the group buying group, and initiator may not know the exactly how many buyers participate the group buying. So we simulate a virtual mall with the realistic data and try to find the suitable group buying model in this environment. Then we examine if participation externality effect, price drop effect and ending effect will appear in this model. Finally, we observe the trend of the number of buyers in group buying to suggest the group buying ending time. The research result indicates that participation externality effect and price drop effect still appear in the Mobile P2P Network environment. But ending effect is not obvious. Because the group buying information is distributed by participating buyers, the distribution will affect the trend of participation and participation externality effect. With suggestion of the system, initiator will not waste much time to wait few participations, and participators can reduce the time cost.

The architecture of certain class of services, such as distributed computing, distributed storages or content delivering networks shifts from the traditional client-server model to more scalable and robust peer to peer networks. Providing proper protection to such complex, open and anonymous systems is very complicated. Malicious peers can cooperate and develop sophisticated strategies to bypass existing security mechanisms. Recently, many trust management systems for P2P networks have been proposed. However, their effectiveness is usually tested only against simple malicious strategies. Moreover, a complex comparison of resistance of a particular method is missing. In this thesis, we (1) propose a new trust management system called BubbleTrust and (2) develop a simulation framework for testing trust management systems against various malicious strategies. Our simulation framework defines several criteria which determine the success of each malicious strategy in the network with a given system. We present results of four trust management systems that represent main contemporary approaches and BubbleTrust.

This research focuses on introducing a novel concept to design a scalable, hierarchical interest-based overlay Peer-to-Peer (P2P) system. We have used Linear Diophantine Equation (LDE) as the mathematical base to realize the architecture. Note that all existing structured approaches use Distributed Hash Tables (DHT) and Secure Hash Algorithm (SHA) to realize their architectures. Use of LDE in designing P2P architecture is a completely new idea; it does not exist in the literature to the best of our knowledge. We have shown how the proposed LDE-based architecture outperforms some of the most well established existing architecture. We have proposed multiple effective data query algorithms considering different circumstances, and their time complexities are bounded by (2+ r/2) only; r is the number of distinct resources. Our alternative lookup scheme needs only constant number of overlay hops and constant number of message exchanges that can outperform DHT-based P2P systems. Moreover, in our architecture, peers are able to possess multiple distinct resources. A convincing solution to handle the problem of churn has been offered. We have shown that our presented approach performs lookup queries efficiently and consistently even in presence of churn. In addition, we have shown that our design is resilient to fault tolerance in the event of peers crashing and leaving. Furthermore, we have proposed two algorithms to response to one of the principal requests of P2P applications’ users, which is to preserve the anonymity and security of the resource requester and the responder while providing the same light-weighted data lookup.

Context. Online piracy is widespread, controversial and poorly understood social phenomena that affects content creators, owners, and consumers. Online piracy, born from recent, rapid ITC changes, raises legal, ethical, and business challenges. Content owners, authors and content consumers should benefit from better understanding of online piracy. Improved, better adapted to marketplace and ITC changes content distribution models should benefit content owners and audiences.Objectives. Investigate online piracy effect on pirated product sales. Improve understanding of online piracy behaviors and process scale.Methods. This observational study investigated movie-sharing effect on U.S. box office. Movie sharing was observed over BitTorrent network, the most popular peer-to-peer file-sharing network. Relationship between piracy and sales was analyzed using linear regression model.Results. File sharing was found to have a slightly positive correlation with U.S. box office sales during first few weeks after film release, and no effect afterwards. Most of newly released movies are shared over BitTorrent network. File sharing is a global, massive phenomenon.Conclusions. I conclude that online movie file sharing has no negative correlation on U.S. box office. Slightly positive movie sharing correlation to box office sales could have occurred because sharing rather informs, than substitutes cinema going.

This research focuses on the redesign of trust and reputation algorithms in the context of hierarchically structured Peer-to-Peer (P2P) networks with Chord, a scalable P2P lookup service for Internet applications. Chord, which is an open source project, is an overlay network based on a distributed hash table(DHT), and all peers in Chord are arranged around a circle. In this work, we propose four adapted trust and reputation algorithms for hierarchically structured P2P networks: EigenTrust, PowerTrust, Absolute Trust and NodeRanking. EigenTrust is one of the most well-known trust and reputation algorithms, as well as the most simple. To calculate the reputation, EigenTrust needs to normalize trust and rely on pre-trusted peers. Like EigenTrust, PowerTrust relies on feedback and the use of a distributed ranking mechanism. It chooses a limited number of power nodes with a high reputation. By combining a random walk strategy and the power nodes, it improves accuracy of global reputation. AbsoluteTrust does not require normalization of trust, pretrusted peers or any centralized authority. Weighted average combined with feedback from peers is employed to determine trust. NodeRanking relies on both individual reputation and social relationship to compute the trust value. NodeRanking evaluates reputation using local information. A node's reputation value can be readily determined by the number of references from other nodes in the network. These adapted algorithms are capable of handling a huge number of nodes disseminated in different rings, which improves complexity and reduces the number of malicious nodes in a hierarchical context. Furthermore, we describe the components of the hierarchical model architecture and present and discuss the results from the experiments. These experiments are employed to verify and compare reduction of downloads from malicious peers, load distribution and residual curl in at structured networks and in hierarchically structured networks.

The main objective of this research is to build an interest based peer – to – peer network which is structured yet non-DHT. Maintaining DHTs is a complex task and needs substantial amount of effort to handle the problem of churn. So, the major challenge facing such architectures is how to reduce this amount of effort while still providing an efficient data query service. The rationale behind choosing non- DHT based interest based network is that users sharing common interests are likely to share similar contents, and therefore searches for a particular type of content is more efficient if peers likely to store that content type are neighbors. We have used a mathematical model based on modular arithmetic, specifically residue class (RC), to design a two-level structured architecture. To the best of my knowledge, there does not exist any such work that has used this mathematical model.

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.

在目前的網際網路中，點對點(P2P)網路的應用扮演了一個重要的角色。由於在點對點網路架構下，檔案分享系統中檔案的數量以及來源大量增加，造成使用者必須花費更多的時間找尋想要的資源，因此搜尋功能就顯得格外地重要。BitTorrent(BT)作為一個點對點檔案分享系統，用戶量不斷增加，已逐漸成為網路頻寬的主要消耗者之一，但是其協定中沒有提供搜尋的功能，而且檔案分散於各個檔案發佈站之間，以及各發佈站之間無法有效搜尋彼此擁有的檔案資源，導致使用者查詢時效率不佳。因此本研究期望建立一套語意式搜尋機制來幫助使用者解決上述的問題。藉由使用語意網技術(Semantic Web)，針對BT檔案分享系統設計本體論，進行資源描述和建立簡單的分類，利用檔案的metadata來提供搜尋的功能以及彙整各檔案分佈站的檔案資源，做為上述議題的一個解決方案，讓使用者能夠更有效率地找到更完整的資源。 / In current World Wide Web, P2P network application plays an important role. Because the number and origin of files increase greatly in file sharing system under the architecture of P2P, causing users to spend more time searching for the resources they want. Therefore, the search function appears especially important. BitTorrent(BT), one kind of P2P file sharing system, has more and more users and becomes one of the biggest consumer of the network bandwidth. But it doesn't support any search function and shared files disperse between many web sites. Furthermore, these web sites can't exchange the shared files they own efficiently. These problems result in inefficient search performance. My research expects to propose a semantic search method to solve the problems mentioned above. By the means of Semantic Web technology, we design the ontology of BT file sharing system to describe the resources and establish simple taxonomy. In addition, using the metadata of files to provide BT for search function and collect the shared files between web sites. Let users find the shared files more efficiently and completely.