Abstract

Mir-BFT (or, simply, Mir) is a robust Byzantine fault-tolerant (BFT) total order broadcast protocol aimed at maximizing throughput on wide-area networks (WANs), targeting deployments in permissioned and Proof-of-Stake permissionless blockchains. Mir is the first BFT protocol that allows a set of leaders to propose request batches independently (i.e., parallel leaders), in a way that precludes request duplication, by rotating the assignment of a partitioned request hash space to leaders. As this mechanism removes a single-leader bandwidth bottleneck and exposes a computation bottleneck related to authenticating clients even on a WAN , our protocol further boosts throughput using client signature sharding optimization. Our evaluation shows that Mir convincingly outperforms state-of-the-art and orders more than 60000 signed Bitcoin-sized (500-byte) transactions per second on a widely distributed 100 nodes, 1 Gbps WAN setup, with typical latencies of few seconds. We also evaluate Mir under different faults, demonstrating its performance robustness.

Mir relies on classical BFT protocol constructs, which simplifies reasoning about Mir correctness. Specifically, Mir is a generalization of the celebrated and scrutinized PBFT protocol. In a nutshell, Mir follows PBFT “safety-wise”, with changes needed to accommodate novel features restricted to PBFT liveness.

Bio:

Marko Vukolic joined IBM Research in January 2015 as a Research Staff Member and earlier was a Post-Doc and Intern in IBM . Before that, he was a faculty in EURECOM , and a visiting professor at Systems Group @ ETH Zurich. He obtained a Doctor of Science (PhD) degree in Distributed Systems from EPFL in the Distributed Programming Laboratory (LPD) in 2008 and an engineering degree in Communication Systems from University of Belgrade in 2001. His research interests lie in the broad area of distributed systems, more specifically fault-tolerance, blockchain and distributed ledgers, cloud computing security and distributed storage.