| The existing BitTorrent's incentive mechanisms, though intended to provide reciprocity and fair exchange, are inefficient in preventing free-riding --- downloading and not uploading in return. There is a fair amount of work, which shows that selfish peers can bypass and exploit BitTorrent incentives. We developed a novel approach intended to discourage peers from free-riding. The main idea behind our approach is authentication of peers by means of a symmetric key protocol based on the Needham-Schroeder protocol. This protocol requires the existence of a trusted third party providing the authentication mechanisms. Additionally, this party will keep track of the amounts of data uploaded and downloaded by each of the peers. In order to demonstrate how our approach affects the BitTorrent file exchange process, we implement a series of experiments simulating the behavior of honest peers and free-riders in the presence and absence of the services provided by a trusted third party. The results of these experiments meet our expectations and prove that the suggested method is efficient. |
