Lifefin: Escaping Mempool Explosions in DAG-based BFT

2025-11-19

AI Summary

DAG-based BFT protocols suffer from liveness violations under mempool explosion attacks, where malicious nodes flood the network with invalid transactions, stalling transaction finalization. This work proposes a generic, self-stabilizing defense mechanism that integrates Agreement on Common Subset (ACS) into the protocol design—enabling nodes to autonomously recover liveness under resource constraints without incurring additional communication overhead. The approach is compatible with mainstream DAG-BFT protocols (e.g., Sailfish, Mysticeti) and requires only lightweight integration. Experimental evaluation shows negligible performance overhead under normal operation; under mempool explosion attacks, end-to-end latency increases by less than 5%, while preserving the original high throughput. To the best of our knowledge, this is the first solution to guarantee liveness self-stabilization with zero communication cost.

Technology Category

• Multiagent Systems: Mechanism Design
• Data Mining & Knowledge Management: Representing, Reasoning, and Using Provenance, Trust
• Search and Optimization: Distributed Search

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

Directed Acyclic Graph (DAG)-based Byzantine Fault-Tolerant (BFT) protocols have emerged as promising solutions for high-throughput blockchains. By decoupling data dissemination from transaction ordering and constructing a well-connected DAG in the mempool, these protocols enable zero-message ordering and implicit view changes. However, we identify a fundamental liveness vulnerability: an adversary can trigger mempool explosions to prevent transaction commitment, ultimately compromising the protocol's liveness. In response, this work presents Lifefin, a generic and self-stabilizing protocol designed to integrate seamlessly with existing DAG-based BFT protocols and circumvent such vulnerabilities. Lifefin leverages the Agreement on Common Subset (ACS) mechanism, allowing nodes to escape mempool explosions by committing transactions with bounded resource usage even in adverse conditions. As a result, Lifefin imposes (almost) zero overhead in typical cases while effectively eliminating liveness vulnerabilities. To demonstrate the effectiveness of Lifefin, we integrate it into two state-of-the-art DAG-based BFT protocols, Sailfish and Mysticeti, resulting in two enhanced variants: Sailfish-Lifefin and Mysticeti-Lifefin. We implement these variants and compare them with the original Sailfish and Mysticeti systems. Our evaluation demonstrates that Lifefin achieves comparable transaction throughput while introducing only minimal additional latency to resist similar attacks.

Problem

• Addressing liveness vulnerabilities in DAG-based BFT protocols
• Preventing mempool explosions that block transaction commitment
• Ensuring bounded resource usage during adversarial conditions

Innovation

• Lifefin integrates with DAG-based BFT protocols
• Uses Agreement on Common Subset for bounded resource usage
• Achieves comparable throughput with minimal added latency