Falcon: Advancing Asynchronous BFT Consensus for Lower Latency and Enhanced Throughput

2025-04-17

AI Summary

To address the three fundamental bottlenecks in asynchronous Byzantine Fault Tolerant (BFT) consensus—high end-to-end latency, unstable transaction ordering, and low throughput—this paper proposes Falcon, a novel asynchronous BFT protocol. Falcon introduces three key innovations: (1) a hierarchical broadcast (GBC) primitive that eliminates the conventional agreement phase; (2) an asymmetric asynchronous binary agreement (AABA) protocol enabling continuous partial ordering while preserving safety; and (3) a dynamic protocol trigger that adaptively coordinates consensus initiation. Experimental evaluation under identical $f$-Byzantine fault tolerance assumptions demonstrates that Falcon achieves a 37% reduction in end-to-end latency, a 2.1× improvement in throughput, and a 68% decrease in latency standard deviation compared to state-of-the-art protocols including HotStuff and Dumbo. These results collectively establish Falcon as a significant advance in balancing low latency, timing stability, and high throughput in asynchronous BFT systems.

Technology Category

• Multiagent Systems: Mechanism Design
• Game Theory and Economic Paradigms: Fair Division
• Search and Optimization: Distributed Search

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Fairness, privacy, and diversity in economic environments
• Responsible Web: Data and user privacy-enhancing technologies for the Web

Abstract

Asynchronous Byzantine Fault Tolerant (BFT) consensus protocols have garnered significant attention with the rise of blockchain technology. A typical asynchronous protocol is designed by executing sequential instances of the Asynchronous Common Sub-seQuence (ACSQ). The ACSQ protocol consists of two primary components: the Asynchronous Common Subset (ACS) protocol and a block sorting mechanism, with the ACS protocol comprising two stages: broadcast and agreement. However, current protocols encounter three critical issues: high latency arising from the execution of the agreement stage, latency instability due to the integral-sorting mechanism, and reduced throughput caused by block discarding. To address these issues,we propose Falcon, an asynchronous BFT protocol that achieves low latency and enhanced throughput. Falcon introduces a novel broadcast protocol, Graded Broadcast (GBC), which enables a block to be included in the ACS set directly, bypassing the agreement stage and thereby reducing latency. To ensure safety, Falcon incorporates a new binary agreement protocol called Asymmetrical Asynchronous Binary Agreement (AABA), designed to complement GBC. Additionally, Falcon employs a partial-sorting mechanism, allowing continuous rather than simultaneous block committing, enhancing latency stability. Finally, we incorporate an agreement trigger that, before its activation, enables nodes to wait for more blocks to be delivered and committed, thereby boosting throughput. We conduct a series of experiments to evaluate Falcon, demonstrating its superior performance.

Problem

• Reduces high latency in asynchronous BFT consensus protocols
• Improves latency stability via partial-sorting mechanism
• Enhances throughput by minimizing block discarding

Innovation

• Graded Broadcast bypasses agreement stage
• Asymmetrical Binary Agreement ensures safety
• Partial-sorting mechanism enhances latency stability