New research by Yunhao Zhang (a fourth year doctoral candidate in computer science), his advisor, Lorenzo Alvisi (Tisch University Professor of Computer Science)—along with Srinath Setty, Qi Chen, and Lidong Zhou at Microsoft Research—was one of three papers to receive the Jay Lepreau Best Paper Award at the 14th USENIX Symposium on Operating Systems Design and Implementation (OSDI) conference. The paper is entitled "Byzantine Ordered Consensus without Byzantine Oligarchy."
The specific order of commands agreed upon when running state machine replication (SMR) is immaterial to fault-tolerance: all that is required is for all correct deterministic replicas to follow it. In the permissioned blockchains that rely on Byzantine fault tolerant (BFT) SMR, however, nodes have a stake in the specific sequence that ledger records, as well as in preventing other parties from manipulating the sequencing to their advantage. The traditional specification of SMR correctness, however, has no language to express these concerns. This paper introduces Byzantine ordered consensus, a new primitive that augments the correctness specification of BFT SMR to include specific guarantees on the total orders it produces; and a new architecture for BFT SMR that, by factoring out ordering from consensus, can enforce these guarantees and prevent Byzantine nodes from controlling ordering decisions (a Byzantine oligarchy). These contributions are instantiated in Pompe, a BFT SMR protocol that is guaranteed to order commands in a way that respects a natural extension of linearizability.