  The very nature of operations in peer-to-peer systems such as BitTorrent
exposes information about participants to their peers. Nodes desiring
anonymity, therefore, often chose to route their peer-to-peer traffic through
anonymity relays, such as Tor. Unfortunately, these relays have little
incentive for contribution and struggle to scale with the high loads that P2P
traffic foists upon them. We propose a novel modification for BitTorrent that
we call the BitTorrent Anonymity Marketplace. Peers in our system trade in k
swarms obscuring the actual intent of the participants. But because peers can
cross-trade torrents, the k-1 cover traffic can actually serve a useful
purpose. This creates a system wherein a neighbor cannot determine if a node
actually wants a given torrent, or if it is only using it as leverage to get
the one it really wants. In this paper, we present our design, explore its
operation in simulation, and analyze its effectiveness. We demonstrate that the
upload and download characteristics of cover traffic and desired torrents are
statistically difficult to distinguish.
