Systems without Cooperation David Levin, University of Maryland Wednesday, March 24 -4:30pm Small Auditorium, CS105 Successful networked systems must account for potentially competing interests: the Internet is no longer the cooperative, technological playground it once was. The protocols are the rules relegating the venue for this competition, but those rules often lack enforcement. I will present the application of economics and trusted hardware to keep participants in a networked system from deviating from the letter and spirit of a protocol. First, I will apply economic mechanism design to keep selfish users from gaining at the expense of others. I will show that the popular BitTorrent system uses, not tit-for-tat as widely believed, but an auction to decide which peers to serve. This model captures known, performance-improving strategies, and shapes or thinking toward new, effective incentive mechanisms. Second, I will apply trusted hardware to keep both selfish and malicious users from "equivocating," or sending semantically conflicting messages. I will present TrInc (Trusted Incrementer), a small piece of trusted hardware intended for use in large-scale distributed systems. With case studies and an implementation, I will demonstrate that TrInc is a practical primitive for protecting a wide range of systems. These two examples together demonstrate the importance of aligning the assumptions of economics and large-scale systems. Doing so allows us to develop new mechanisms that foster cooperation among the otherwise self-interested.