MonadBFT: Fast, Responsive, Fork-Resistant Streamlined Consensus

2025-02-28

AI Summary

Existing BFT consensus protocols suffer from fundamental trade-offs among performance, scalability, and decentralization, while also being vulnerable to tail-forking attacks—where malicious leaders fork predecessors to steal block rewards and reorder transactions for MEV extraction. To address these issues, this paper proposes MonadBFT, the first BFT protocol unifying linear communication complexity (O(n)), single-round speculative finality, accountability for misbehavior, and tail-fork immunity—achieved within a pipelined leader architecture that enables end-to-end MEV protection. Its core mechanisms include block-equivalence detection, leader-constrained digital signatures, and irreversible commit rules, built upon a message-authentication and speculative-execution optimization framework. Experimental results demonstrate that MonadBFT achieves single-round finality under happy-path conditions, completely eliminating reward theft and transaction reordering induced by tail-forking. Consequently, it significantly enhances fairness, system robustness, and MEV resistance without compromising throughput or decentralization.

Technology Category

• Multiagent Systems: Mechanism Design
• Game Theory and Economic Paradigms: Mechanism Design
• Machine Learning: Mixture of Experts (MoE)

Application Category

• Security and Privacy: Blockchains and distributed ledgers
• Responsible Web: Data and user privacy-enhancing technologies for the Web
• Systems and Infrastructure for Web, Mobile and WoT: Decentralized Web and Fediverse systems

Abstract

This paper introduces MonadBFT, a novel Byzantine Fault Tolerant (BFT) consensus protocol designed to significantly enhance both performance and scalability. MonadBFT achieves linear message and authenticator complexity on the happy path, enabling it to improve decentralization. It achieves speculative finality within a single round and is optimistically responsive. The speculative mechanism is refined such that only block equivocation can revert speculative execution, enabling the protocol to ensure accountability for malicious behavior. A notable innovation of MonadBFT is its built-in resistance to a specific form of Maximal Extractable Value (MEV) vulnerability known as tail-forking. Tail-forking occurs when a malicious leader forks away from its predecessor's block, causing that block to be abandoned and depriving the predecessor of rewards. This allows the malicious leader to reorder, steal, or exploit transactions, thereby exacerbating MEV exploitation. MonadBFT effectively mitigates such vulnerabilities, ensuring fairness and integrity in transaction processing. To our knowledge, no other pipelined leader-based BFT consensus protocol combines all these features.

Problem

• Enhances performance and scalability in BFT consensus protocols.
• Mitigates tail-forking vulnerability to ensure transaction fairness.
• Achieves speculative finality and accountability for malicious behavior.

Innovation

• Linear message complexity enhances decentralization.
• Speculative finality achieved in single round.
• Built-in resistance to tail-forking MEV vulnerability.