Perhaps the archetypical trilemma is consensus - it requires three properties: agreement, liveness, and validity. Getting any two is easy, but all three together is what makes consensus such a facinating problem that continues to create new challenges even after 40 years of research. A lot of research focuses on...| decentralizedthoughts.github.io
In the first part of this post, we describe a single-shot variation of Two Round HotStuff (see HotStuff v1 paper, March 2018 and this March 2018 post) using Locked-Broadcast that follows a similar path as our previous posts on Paxos and Linear PBFT. In the second part, we describe a...| decentralizedthoughts.github.io
Since 2018, blockchain research has seen a surge in DAG-based BFT protocols aimed at achieving higher throughput. These protocols trace back to Hashgraph, 2018, Aleph, 2019, the theoretical work of All You Need is DAG, 2021, and systems papers like Narwhal and Bullshark. In this post, we highlight six key...| decentralizedthoughts.github.io
PBFT is a foundational multi-year project led by Barbara Liskov and her students, obtaining major advances in both the theory and practice of Byzantine Fault Tolerance. The PBFT conference version, journal version, Castro’s thesis, Liskov’s talk, and follow-up work on BASE are all required reading for anyone who wants to...| decentralizedthoughts.github.io
In this post, we will present (a variant of) PBFT, which is the first practical solution to Byzantine fault tolerant state machine replication under partial synchrony. The protocol follows the key ideas presented in the previous post on partial synchrony. Setting There are $n$ parties, at most $t<n/3$ of them...| decentralizedthoughts.github.io
In this post, we show how to solve Validated Asynchronous Byzantine Agreement using the multi-world VABA approach from Abraham, Malkhi, and Spiegelman 2018. What is Validated Asynchronous Byzantine Agreement? Given $n$ parties, with at most $f < n/3$ malicious (the optimal ratio for consensus with asynchronous communication), parties share an...| decentralizedthoughts.github.io
We recently published our work HotStuff-2 on eprint, introducing a two-phase HotStuff variant which simultaneously achieves $O(n^2)$ worst-case communication, optimistically linear communication, a two-phase commit regime within a view, and optimistic responsiveness in partially-synchronous BFT. The main takeaway is that two phases are enough for BFT after all. In this...| decentralizedthoughts.github.io
