BitStore : An Incentive-Compatible Solution for Blocked Downloads in BitTorrent

As many as 30% of all files shared on public BitTorrent networks suffer from the lack of “seeders” (peers that have complete copies of the file being shared); peers attempting to download such a file (“leechers”) may have to wait indefinitely to obtain certain file chunks that are not distributed in the file’s network of peers (the “swarm”). We call this the Blocked Leecher Problem (BLP). To alleviate BLP, we propose BitStore, a larger, secure network of BitTorrent users (not necessarily all sharing the same content) where nodes offer their resources (such as disk space and bandwidth) for public use. Peers sharing any file can use the storage network to maintain replicas for each chunk of the file. Any leecher seeking chunks that are absent from in its own swarm can query the public network, locate the node storing the said chunks, and retrieve them. BitStore also provides robust incentives for nodes contributing resources: In return for storing and serving chunks, such nodes can negotiate micropayments using a second-price auction. Peers who receive these credits may later use them to retrieve blocks they need from the storage network. This paper quantifies the BLP, presents an overview of the BitStore design, and discusses various challenges related to storage management and incentives.