Scalable Byzantine Fault Tolerance via Partial Decentralization

TL;DR

This paper introduces DQBFT, a new scalable Byzantine Fault Tolerance paradigm that decentralizes command replication and centralizes ordering, achieving significant performance improvements in geo-distributed blockchain environments.

Contribution

The paper presents DQBFT, a novel BFT protocol framework that addresses scalability and performance issues by dividing consensus into replication and ordering, and introduces Destiny, a specific protocol utilizing trusted subsystems and threshold signatures.

Findings

3x higher throughput than previous protocols

50% reduction in latency

Effective in geo-distributed deployments

Abstract

Byzantine consensus is a critical component in many permissioned Blockchains and distributed ledgers. We propose a new paradigm for designing BFT protocols called DQBFT that addresses three major performance and scalability challenges that plague past protocols: (i) high communication costs to reach geo-distributed agreement, (ii) uneven resource utilization hampering performance, and (iii) performance degradation under varying node and network conditions and high-contention workloads. Specifically, DQBFT divides consensus into two parts: 1) durable command replication without a global order, and 2) consistent global ordering of commands across all replicas. DQBFT achieves this by decentralizing the heavy task of replicating commands while centralizing the ordering process. Under the new paradigm, we develop a new protocol, Destiny that uses a combination of three techniques to achieve high performance and scalability: using a trusted subsystem to decrease consensus's quorum size, using threshold signatures to attain linear communication costs, reducing client communication. Our evaluations on 300-replica geo-distributed deployment reveal that DQBFT protocols achieve significant performance gains over prior art: $\approx$3x better throughput and $\approx$50\% better latency.