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A Reputation System for Bittorrent Peer-To-Peer File-Sharing Networks

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A Reputation System for Bittorrent Peer-To-Peer File-Sharing Networks University of Wollongong Thesis Collections University of Wollongong Thesis Collection University of Wollongong Year A reputation system for BitTorrent peer-to-peer file-sharing networks Lan Yu University of Wollongong Yu, Lan, A reputation system for BitTorrent peer-to-peer file-sharing networks, M.Comp.Sc. thesis, Information Technology and Computer Science, University of Wollongong, 2006. http://ro.uow.edu.au/theses/637 This paper is posted at Research Online. http://ro.uow.edu.au/theses/637 NIVERSITY U OF WOLLONGONG A Reputation System for BitTorrent Peer-to-Peer File-sharing Networks A thesis submitted in fulfillment of the requirements for the award of the degree Master of Computer Science by Research from UNIVERSITY OF WOLLONGONG by Lan YU Faculty of Informatics August 2006 c Copyright 2006 by Lan YU All Rights Reserved ii Dedicated to My family iii Declaration This is to certify that the work reported in this thesis was done by the author, unless specified otherwise, and that no part of it has been submitted in a thesis to any other university or similar institution. Lan YU August 31, 2006 iv Abstract Over the past few years, Peer-to-Peer (P2P) networks have grown extensively and dramatically changed large-scale file transfer. One of the most popular P2P network is the BitTorrent system. BitTorrent can efficiently distribute large files by optimiz- ing the use of network bandwidth and providing scalability. Due to the open and anonymous nature of P2P systems BitTorrent also provides an ideal environment for distribution of malicious, low quality, or doctored information. A number of reputation systems, including P2PRep with its successors XRep and X2Rep, had been proposed to address security weaknesses of Gnutella P2P file sharing networks. Although it has been claimed that these methods are also applicable to the other file sharing networks, it is not clear how to achieve this task. Moreover, some of the shortcomings of these reputation systems such as online-polling only and cold-start may be exploited by ma- licious attackers. In this paper, we propose a reputation system, called X2BTRep, which is an extension of the X2Rep and for BitTorrent network. We show that the proposed system improves the security and the quality of information distributed over P2P networks. v Acknowledgements First of all, I would like to make a grateful acknowledgement to Rei Safavi-Naini, my supervisor, for pointing me to the right direction on my research, Network Security in Peer to Peer System. During this research, she provided me many valuable advices and constant support. Also, my sincere appreciation goes to Willy Susilo, my co-supervisor, for his guidance through the past two years of chaos and confusion on my study and life. Moreover, I am thankful to Juliet Richardson, International Study Program Coor- dinator, for her carefully reading the draft and offering grammar correcting and writing suggestions. Additionally, my thanks go to all staff in my Faculty, School of Information Tech- nology and Computer Science, for their offering many facilities, including space,soft and hardware, telephone, etc. to support my research. Furthermore, I appreciated my family and friends for their encouragement helping me to finish this research. vi Publications L. Yu. X2BTRep trusted reputation system: A robust mechanism for P2P networks. HDR Student Conference, University of Wollongong, Australia, August 2006. L. Yu, W. Susilo, and R. Safavi-Naini. X2BTRep trusted reputation system: A robust mechanism for P2P networks. The 5th International Conference on Cryptology and Network Security, China, August 2006. vii Contents Abstract v Acknowledgements vi Publications vii 1 Introduction 1 1.1 AimsandObjectives ............................ 2 1.2 StructureoftheThesis ........................... 3 1.3 OurContribution .............................. 3 1.4 Glossary................................... 4 1.5 Notations .................................. 4 2 Peer-to-Peer: Now and the Future 6 2.1 WhatisaP2PNetwork?.......................... 6 2.2 Generational Evolution of P2P Networks . ... 8 2.2.1 FirstGeneration–CentralisedP2P . 8 2.2.2 Second Generation – Decentralised P2P . 11 2.2.3 ThirdGeneration–HybridP2P . 14 2.2.4 CurrentDevelopments . 17 2.3 Advantages and Weaknesses of P2P Networks . .. 20 2.4 Summary .................................. 22 3 Previous Studies of Reputation Systems 23 3.1 Introduction................................. 23 3.2 eBay..................................... 23 3.3 P2PRep ................................... 25 3.4 XRep..................................... 29 3.5 X2Rep.................................... 31 viii 3.6 Credence................................... 33 3.7 Summary .................................. 35 4 Overview of BitTorrent Network 37 4.1 Introduction................................. 37 4.2 Architecture................................. 37 4.3 ProtocolSpecification. 39 4.3.1 Bencoding.............................. 39 4.3.2 MetainfoFile(.torrentfile). 40 4.3.3 TrackerHTTPprotocol . 41 4.3.4 PeerTCPProtocol ......................... 43 4.4 StrengthsofBitTorrent. 45 4.5 ShortcomingsofBitTorrent . 46 4.5.1 Distributionoffalseinformation . .. 46 4.5.2 Man-in-middleattack. 47 4.5.3 IPharvesting ............................ 47 4.6 Summary .................................. 48 5 A Robust Reputation Management System – X2BTRep 49 5.1 Introduction................................. 49 5.2 Principle of our Management Model . 49 5.2.1 Assumptions............................. 49 5.2.2 DistributedRepositories . 50 5.2.3 Voting ................................ 50 5.2.4 CentralisedRepositories . 51 5.2.5 SecureSocketsLayer . 51 5.3 Further Discussion of Two Novel Algorithms . .... 51 5.3.1 Credibility Award Algorithm . 52 5.3.2 Credibility Chain Exchange . 52 5.4 ProtocolDesigns .............................. 53 5.4.1 Initialisation Phase: Enhanced Torrent Creation . ...... 53 5.4.2 Phase1:TorrentSearch . 54 5.4.3 Phase2:ExchangeofVotes . 54 5.4.4 Phase3:VotesEvaluation.. 55 5.4.5 Phase4:TrackerQueries. 57 5.4.6 Phase 5: Pieces and Credibility Chain Exchange . ... 57 ix 5.4.7 Phase 6: Updating and Voting Reputation Value . 58 5.5 Summary .................................. 59 6 Critical Evaluation of X2BTRep 60 6.1 Introduction................................. 60 6.2 Assessment of X2BTRep.......................... 60 6.3 Attacks on BitTorrent-like systems . ... 62 6.3.1 Defectionattack........................... 62 6.3.2 Poisoning attack & Insertion of viruses in carried data ..... 62 6.3.3 Denialofserviceattack. 62 6.3.4 Malware software in BitTorrent networks . .. 63 6.3.5 Identityattack ........................... 63 6.3.6 Spamming.............................. 63 6.4 Attacks on Reputation-based Systems . ... 63 6.4.1 Pseudospoofing ........................... 63 6.4.2 Reputationspoofing . .. .. 64 6.4.3 Whitewashingattack . 64 6.4.4 Reputationattackbycollectives . 64 6.4.5 Referralattack ........................... 65 6.5 Summary .................................. 65 7 Implementation and Interpretation of Experiment 67 7.1 Introduction................................. 67 7.2 Implementation of X2BTRep in the BitTorrent Environment . 67 7.2.1 X2BTRepExtensionstoBitTorrent . 67 7.2.2 RepositorySchema . .. .. 69 7.2.3 AdditionalProtocolMessages . 70 7.3 Experiment ................................. 71 7.3.1 I.IntentionofExperiment . 71 7.3.2 II.ExperimentSetting . 71 7.3.3 III.WorkingPrinciple . 72 7.3.4 IV.MaliciousStrategies . 73 7.3.5 V.SimulationResult . 75 7.3.6 VI. Conclusion of Our Experiment . 77 7.4 Comparison with other Reputation Systems . ... 78 7.5 Summary .................................. 80 x 8 Conclusions and Future Work 81 Bibliography 84 xi List of Tables 2.1 The definition of five descriptors in the Gnutella protocol........ 13 3.1 The basic polling protocol in P2PRep system . ... 27 3.2 The enhanced polling protocol in P2PRep system . .... 28 3.3 The X2Repreputationsystemprotocol . 32 3.4 The summary of various trusted reputation mechanisms . ....... 36 7.1 The summary of a comparison between X2BTRep and other trust rep- utationmechanisms............................. 79 xii List of Figures 2.1 First Generation – Centralised P2P Architecture . ....... 9 2.2 Sequence of operations in the Napster protocol . ...... 10 2.3 Second Generation – Decentralised P2P Architecture . ....... 12 2.4 Sequence of operations in the Gnutella v0.4 protocol . ....... 13 2.5 Third Generation – Hybrid P2P Architecture . ... 15 4.1 BitTorrentArchitecture. 38 4.2 A glance at torrent files of Linux from mininova.org webpage. 39 5.1 Sequence of messages in enhanced torrent creation phase ........ 53 5.2 Number of active peers over time (sourced from [26]) . ...... 55 5.3 Sequence of messages and operations in X2BTRep protocol . 56 7.1 BitTorrent’s Information Flow with X2BTRep protocol extensions . 68 7.2 Basic working principle based on a genuine resource and honest clients 72 7.3 Working principle based on a milicious resource and honest clients . 74 7.4 Working principle based on a malicious resource and several dishonest pollers .................................... 75 7.5 Simulation results in different situations . ...... 76 xiii Chapter 1 Introduction Peer-to-peer (P2P) file sharing is one of the most significant technical models of the internet. Rather than traditional client-server architecture, P2P networks equip each node with an equivalent capability or responsibility and they can share computer re- sources and services via direct connections. Over
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