A simple yet remarkably powerful tool of selfish and malicious participants in a distributed system is “equivocation”: making conflicting statements to others. We present TrInc, a small, trusted component that combats equivocation in large, distributed systems. Consisting fundamentally of only a non-decreasing counter and a key, TrInc provides a new primitive: unique, once-in-alifetime attestations.

We show that TrInc is practical, versatile, and easily applicable to a wide range of distributed systems. Its deployment is viable because it is simple and because its fundamental components—a trusted counter and a key—are already deployed in many new personal computers today. We demonstrate TrInc’s versatility with three detailed case studies: attested append-only memory (A2M), PeerReview, and BitTorrent.

We have implemented TrInc and our three case studies using real, currently available trusted hardware. Our evaluation shows that TrInc eliminates most of the trusted storage needed to implement A2M, significantly reduces communication overhead in PeerReview, and solves an open incentives issue in BitTorrent. Microbenchmarks of our TrInc implementation indicate directions for the design of future trusted hardware.