SoK: Design Choices in Tendermint BFT Consensus

Abstract

Tendermint is a consensus protocol that tolerates Byzantine faults, implemented first by the Tendermint Core engine and now by CometBFT. Realizing the protocol's separation of agreement from execution, the Application Blockchain Interface (ABCI) of these engines keeps consensus apart from the replicated application, so one engine can serve many independent proof-of-stake chains. A sustained body of research proposes changes that span the protocol's mechanisms, from vote dissemination to block proposal and reward distribution, yet to our knowledge no survey studies the protocol and these works as one family, and broader surveys do not take Tendermint as their subject. We describe the baseline, the protocol as consolidated from its original descriptions, by its design choices. Each is a decision, such as how votes spread or how proposers rotate, through which the baseline provides safety and liveness or another property under its fault and timing model. We classify each work by the design choice it renegotiates, that is, modifies or replaces, by the properties it strengthens or weakens, and by whether its result needs a stronger model. Taking a broader perspective on that classification, we group the surveyed works' solutions into a few threads of concern in the baseline, namely its performance, the accountability of its validators, and the protection of exploitable information. For each thread, we identify the recurring strategies that their approaches follow. Together, these threads and strategies describe the current state of research on the Tendermint family. Where the strategies leave gaps, we pose future directions, each as an open question under an explicit fault and timing model.