1 Introduction Establishing trust is a fundamental problem in distributedsystems. Peer-to-peer systems, in which service functionality is distributed across clients, eliminate the cen-tralized components that have traditionally functioned as de facto trust brokers, and consequently exacerbate trust-related problems. When peers lack meaningful measures on which to base trust decisions, they end up receivingservices from untrustworthy peers, with e ffects that canrange from wasted resources on mislabeled content to

Abstract — BitTorrent (BT) in the last years has been one of the most effective mechanisms for P2P content distribution. Although BT was created for distribution of time insensitive content, in this work we try to identify what are the minimal changes needed in the BT’s mechanisms in order to support streaming. The importance of this capability is that the peer will now have the ability to start enjoying the video before the complete download of the video file. This ability is particularly important in highly polluted environments, since the peer can evaluate the quality of the video content early and thus preserve its valuable resources. In a nutshell, our approach gives higher download priority to pieces that are close to be reproduced by the player. This comes in contrast to the original BT protocol, where pieces are downloaded in an out-of-order manner based solely on their rareness. In particular, our approach tries to strike the balance between downloading pieces in: (a) playing order, enabling smooth playback, and (b) the rarest first order, enabling the use of parallel downloading of pieces. In this work, we introduce three different Piece Selection mechanisms and we evaluate them through simulations based on how well they deliver streaming services to the peers. I.

Real-world IP applications such as Peer-to-Peer filesharing are now able to benefit from network and location awareness. It is therefore crucial to understand the relation between underlay and overlay networks and to characterize the behavior of real users with regard to the Internet. For this purpose, we have designed and implemented MULTIPROBE, a framework for large-scale P2P file-sharing measurements. Using this framework, we have performed measurements of BitTorrent, which is currently the P2P file sharing network with the largest amount of Internet traffic. We analyze and correlate these measurements to provide new insights into the topology, the connectivity, and the path characteristics of the Internet parts underlying P2P networks, as well as to present unique information on the BitTorrent throughput and connectivity.

Abstract. We present a trust-based mechanism for the acquisition of information from possibly unreliable sources. Our mechanism addresses the case where the acquired information cannot be verified. The idea is to intersperse questions (“challenges”) for which the correct answers are known. By evaluating the answers to these challenges, probabilistic conclusions about the correctness of the unverifiable information can be drawn. Less challenges need to be used if an information provider has shown to be trustworthy. This work focuses on three major issues of such a mechanism. First, how to estimate the correctness of the unverifiable information. Second, how to determine an optimal number of challenges. And finally, how to establish trust and use it to reduce the number of challenges. Our approach can resist collusion and shows great promise for various application areas such as distributed computing or peer-to-peer networks.

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This paper offers a survey of the emerging field of private peer-to-peer networks, which can be defined as internet overlays in which the resources and infrastructure are provided by the users, and new users may only join by personal invitation. The last few years have seen rapid developments in this field, many of which have not previously been described in the research literature. We describe deployed systems, classify them architecturally, and identify some technical and social tradeoffs in the design of private peer-to-peer networks.

Anti-P2P companies have begun to launch Internet attacks against BitTorrent swarms. In this paper, we analyze how successful these attacks are at impeding the distribution of targeted files. We present the results of both passive and active measurements. For our active measurements, we developed a crawler that contacts all the peers in any given swarm, determines whether the swarm is under attack, and identifies the attack peers in the swarm. We used the crawler to analyze 8 top box-office movies. Using passive measurements, we performed a detailed analysis of a recent album that is under attack. 1.

Abstract. In this paper we propose an analytical model for file diffusion in a peer-to-peer (P2P) file-sharing network based on biological epidemics. During the downloading process, the peer shares the downloaded parts of the file and, thus, contributes to distributing it in the network. This behavior is similar to the spreading of epidemic diseases which is a well researched subject in mathematical biology. With our model we investigate the dynamics of file diffusion focusing on the effects of pollution, e.g. malicious peers sharing corrupted version of the file. 1

applications for many users. With millions of users world-wide sharing music, video, software, and pictures 1, file movement on these networks represent a significant percentage of internet traffic. Beyond the much discussed copyright infringement issues, P2P networks threaten both corporate and individual security. Our research shows that confidential and potentially damaging documents have made their way onto these networks and continue to do so. The research also shows that criminals trawl P2P networks and opportunistically exploit information that they find. P2P file sharing represents a growing security threat because of the evolution of these networks. Internet service providers (ISPs), firms, and copyright holders have responded to the rise of P2P both technically (site blocking, traffic filtering and content poisoning 2) and legally. These challenges have prompted P2P developers to create decentralized, encrypted, anonymous networks that are difficult to track, are designed to accommodate large numbers of clients, and are capable of transferring vast amounts of data. We analyze the P2P security issues, establishing the vulnerabilities these software clients represent. Then we present experimental evidence of the risk through honeypot experiments that expose both business and personal financial information and track the resulting consequences. This analysis and experimental results clearly show the security risk of P2P file sharing networks. * We are grateful for the assistance of Tiversa Inc and Scott Dynes of the Center for Digital Strategies at the Tuck School. Experiments described in this paper were conducted in collaboration with Tiversa who has developed a patent pending technology that, in real-time, monitors global P2P file sharing networks. This work was supported under Award number 2000-DT-CX-K001 from the Office for Domestic Preparedness, Department of Homeland Security. Points of view in this document are those of the authors and do not necessarily represent the official position of the U.S. Department of Homeland Security.

foundation industry studies fellowship. Converting Pirates without Cannibalizing Purchasers: