Fast Tendermint: Speeding Up a Foundational Consensus Protocol

2026-08-13

AI Summary

This work addresses the high transaction confirmation latency of the traditional Tendermint consensus protocol, which requires three communication rounds in partially synchronous networks. The authors propose an optimized variant that preserves Tendermint’s rotating-leader mechanism and core structure while relaxing the fault-tolerance bound to $n > 5f$. By merging the prevote and precommit phases and unifying the locked and valid states, the protocol reduces the normal-case consensus to two rounds. Using the formal modeling language Quint, the authors provide a rigorous specification and model-checking verification, formally proving the protocol’s safety—encompassing consistency and validity—and liveness under the $n > 5f$ condition. This advancement establishes a new, efficient paradigm for low-latency Byzantine fault-tolerant blockchains.

Abstract

Tendermint is among the most widely studied and deployed Byzantine fault-tolerant (BFT) consensus protocols, owing in part to its native leader-rotation mechanism that subsumes complex view changes. Like most partially-synchronous BFT protocols, Tendermint tolerates $f < n/3$ Byzantine processes and decides in three communication steps. Motivated by the push for lower-latency blockchains, a recent line of work shows that consensus can be solved in two communication steps when $f < n/5$. We present Fast Tendermint, an adaptation of Tendermint to the $n > 5f$ setting that decides in two communication steps in the good case, while preserving Tendermint's leader-rotation structure. Fast Tendermint collapses Tendermint's prevote and precommit steps into a single voting step and merges the $locked$ and $valid$ state. We give proofs of agreement, validity, and termination, and a formal specification in Quint, a modern surface syntax for TLA+, used to model-check the protocol.

Problem

• Byzantine fault tolerance
• consensus protocol
• Tendermint
• low-latency blockchain
• communication steps

Innovation

• Fast Tendermint
• Byzantine fault tolerance
• two-step consensus
• leader rotation
• formal verification