Master Thesis
Fast Paths in BFT Consensus: A Comparative Framework
Fast finalization is a recurring goal in Byzantine fault-tolerant (BFT) consensus: when conditions are favorable, a protocol may try to commit in fewer rounds than its standard execution. One way to achieve this is through a dedicated fast path, that is, an optimistic execution path that succeeds only under stronger assumptions or with extra resources. FaB Paxos [1] initiated this line of work, and later results refined its resilience bounds and clarified which optimistic latencies are achievable in closely related broadcast settings [2, 3]. More recent protocols such as Banyan [4] and Kudzu [5] revisit these ideas in modern BFT protocol designs.
This thesis asks the question: under which assumptions does a fast path exist in BFT consensus, and what does it cost? The student will compare a selected corpus of protocols in a common framework, focusing on dimensions such as synchrony assumptions, fault thresholds, quorum structure, replica count, and optimistic latency. A central part of the work will be to reconcile terminology and assumptions across papers so that the comparison is precise rather than merely descriptive.
The expected outcome is a structured taxonomy of fast-path designs and their trade-offs. The thesis should clarify which costs appear to be fundamental, which are tied to specific models, and where recent protocols genuinely improve over classical constructions. A strong thesis may also identify open gaps or mismatches in the literature, but the primary goal is a structured comparative framework that makes the design space easier to understand.
References
[5] Victor Shoup, Jakub Sliwinski, and Yann Vonlanthen. Kudzu: Fast and Simple High-Throughput BFT. 39th International Symposium on Distributed Computing (DISC 2025). (talk from Victor Shoup)