Beluga: Block Synchronization for BFT Consensus Protocols
Tasos Kichidis, Lefteris Kokoris-Kogias, Arun Koshy, Ilya Sergey, Alberto Sonnino, Mingwei Tian, Jianting Zhang

TL;DR
Beluga introduces a block synchronizer abstraction for BFT consensus protocols, enhancing efficiency and security, demonstrated by its integration into the Sui blockchain, which improves performance and resilience under attack.
Contribution
It proposes a novel block synchronizer concept for BFT protocols, providing a resource-aware, efficient, and attack-resilient block exchange mechanism.
Findings
Achieves optimal latency in normal conditions
Provides up to 3x higher throughput under attack
Reduces latency by 25x compared to prior designs
Abstract
Modern high-throughput BFT consensus protocols use streamlined push-pull mechanisms to disseminate blocks and keep happy-path performance optimal. Yet state-of-the-art designs lack a principled and efficient way to exchange blocks, which leaves them open to targeted attacks and performance collapse under network asynchrony. This work introduces the concept of a block synchronizer, a simple abstraction that drives incremental block retrieval and enforces resource-aware exchange. Its interface and role fit cleanly inside a modern BFT consensus stack. We also uncover a new attack, where an adversary steers honest validators into redundant, uncoordinated pulls that exhaust bandwidth and stall progress. Beluga is a modular and scarcity-aware instantiation of the block synchronizer. It achieves optimal common-case latency while bounding the cost of recovery under faults and adversarial…
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Taxonomy
TopicsDistributed systems and fault tolerance · Interconnection Networks and Systems · Network Time Synchronization Technologies
