Set Byzantine Consensus Decentralizes Rollup Sequencers and Data Availability ∞ Research

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Briefing

The research addresses the critical centralization risk inherent in Layer 2 rollup architectures, where a single-node sequencer is a primary point of failure and censorship. It proposes a fully decentralized “arranger” service that unifies the sequencer and the Data Availability Committee (DAC) roles. The foundational breakthrough is the application of Set Byzantine Consensus (SBC) , a protocol that achieves agreement on a subset of proposed transaction batches, thereby eliminating the single-node bottleneck. The single most important implication is the creation of provably robust, censorship-resistant rollup systems that maintain high throughput without sacrificing decentralization.

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Context

Prior to this work, the prevailing architecture of optimistic and ZK rollups relied on a centralized sequencer to order and batch transactions before committing them to Layer 1. This established model created a “decentralization bottleneck,” exposing the system to risks like transaction censorship, liveness failure (halting the L2), and the extraction of Maximal Extractable Value (MEV) by the sequencer operator. The challenge was to achieve decentralized ordering without compromising the speed required for pre-confirmations, as a single, trusted entity was computationally simpler.

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Analysis

The core mechanism is the Decentralized Arranger powered by Set Byzantine Consensus (SBC). The Arranger is a distributed service responsible for both sequencing transactions and ensuring data availability. Conceptually, SBC works by having multiple participants propose sets of transaction requests. The protocol then formally reaches consensus on a specific subset of the union of all proposed sets.

This differs from traditional Byzantine Fault Tolerance (BFT) consensus, which aims for agreement on a single, fixed sequence. By agreeing on a set of valid batches and their ordering, the Arranger can post compressed transaction hashes to L1, with the DAC function (also decentralized within the Arranger) providing the necessary data for verification. This modular, set-based agreement fundamentally distributes the power of transaction ordering.

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Parameters

Decentralization Bottleneck ∞ Eliminated. The centralized sequencer, a single point of trust and failure in prior L2 architectures, is replaced by a distributed Set Byzantine Consensus mechanism.

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Outlook

This research immediately opens new avenues for modular blockchain design, specifically the creation of shared sequencer networks that can service multiple rollups simultaneously. In the next 3-5 years, this theoretical model is likely to unlock real-world applications in “plug-and-play” decentralized sequencer services, significantly lowering the barrier for new Layer 2s to launch with full censorship resistance and liveness guarantees. The work establishes a formal framework for defining and proving the correctness of these combined sequencing and data availability services.

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Verdict

The formal application of Set Byzantine Consensus to rollup sequencing is a foundational shift, transforming Layer 2s from semi-decentralized systems into fully robust, trust-minimized architectures.

Decentralized sequencer, rollup architecture, set consensus, data availability, MEV mitigation, censorship resistance, L2 scaling, Byzantine fault tolerance, transaction ordering, consensus mechanism, single point failure, liveness guarantee, modular blockchain, shared sequencer Signal Acquired from ∞ arxiv.org