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On the Feasibility of Using Probably Approximately Correct Search Over BitTorrent Tracking Information

22 March 2013

William Mayor

This central focus point for the protocol creates a security weak spot that can be exploited. Distrupting the tracker’s service effectively halts the running of the entire BitTorrent network. In order to improve on these concerns the Distributed Hash Table (DHT) extension has been introduced and widely adopted. The DHT spreads the responsibilities of the tracker across the network and so mitigates the problems of a disrupted tracker. Whilst this improves the security of BitTorrent it has had some unintended side effects that may weaken the system’s resistance to censorship. It is possible for an attacker to focus an attack on particular elements of the DHT and in doing so censor those elements. As an alternative to a DHT, Probably Approximately Correct (PAC) search can also be used to retrieve data from distributed networks. PAC uses an unstructured distributed peer- to-peer architecture where it is assumed that it is possible to randomly sample nodes in the network. Such an architecture is expected to be more resistant to attack. This paper aims to investigate existing BitTorrent networks in order to determine how best to apply PAC search. This study also aims to reveal the extent to which a PAC solution can emulate current information retrieval performance. It is recognised that PAC search is unlikely to be able to perform as well as existing BitTorrent solutions. In light of this the study aims to examine whether there is a reasonable compromise to be made between retrieval performance and security.