Blockmania: from Block DAGs to Consensus

TL;DR

Blockmania introduces a leaderless Byzantine consensus protocol using block DAGs that achieves high throughput, low communication complexity, and robustness, suitable for dynamic and proof-of-stake networks.

Contribution

It presents a novel block DAG-based consensus protocol with low communication complexity and high efficiency, outperforming traditional protocols like PBFT.

Findings

Achieves over 400K transactions per second in wide area networks

Has communication complexity of O(N^2) with low constants

Includes a variant with O(N) communication cost and O(log N) latency

Abstract

Blockmania is a byzantine consensus protocol. Nodes emit blocks forming a directed acyclic graph (block DAG) that is subsequently interpreted by each node separately to ensure consensus with safety, liveness and finality. The resulting system has communication complexity $O(N^2)$ even in the worse case, and very low constant factors --- as compared to $O(N^4)$ for PBFT; it is leaderless; and network operations do not depend on the composition of the quorum or node stake. This makes Blockmania very efficient (leading to over 400K transactions per second on a wide area network), and ideal for dynamic membership and flexible and non-interrupted proof-of-stake protocols. A X-Blockmania variant, has $O(N)$ communication cost but also higher latency $O(\log N)$.