Briefing
The centralization risk and MEV extraction inherent in Layer 2 sequencers present a systemic vulnerability to the modular blockchain paradigm. This research proposes a foundational shift to Shared Sequencer Networks (SSNs) , utilizing a decentralized consensus mechanism ∞ often BFT-based with threshold cryptography ∞ to order transactions across multiple rollups simultaneously. This new architectural primitive enforces atomic cross-rollup transactions , thereby eliminating the arbitrage opportunities that constitute cross-rollup MEV and establishing a new standard for decentralized interoperability and economic fairness in the multi-rollup ecosystem.
Context
The prevailing architecture for Layer 2 rollups relies on a single, centralized sequencer to order and batch transactions, which introduces a single point of failure and a persistent monopoly on transaction ordering. This centralized control creates a structural limitation ∞ it allows the sequencer to extract local MEV and, crucially, prevents the atomic execution of transactions spanning different rollups. This fragmentation generates the systemic risk of cross-rollup MEV , where profit-seeking actors exploit the time delay between related transactions on separate chains, a challenge that is fundamentally game-theoretic and not merely technical.
Analysis
The core idea introduces a dedicated, decentralized sequencing layer that operates as a single, unified ordering service for multiple independent rollups. This layer replaces the individual centralized sequencers with a set of BFT-secured, rotating operators elected via delegated staking. The mechanism’s breakthrough is the enforcement of atomic data inclusion , where transaction data from all participating rollups is included in the shared sequence block simultaneously. This shared, cryptographically-secured ordering guarantees that a transaction spanning two rollups is either executed completely or not at all, conceptually achieving multi-domain atomicity and removing the exploitable time-ordering gap.
Parameters
- Guaranteed Finality Latency ∞ 12 ∞ 18 seconds ∞ The time required for the decentralized sequencing layer to finalize a block of cross-rollup transactions, providing a concrete performance metric for trustless interoperability.
Outlook
The realization of a truly decentralized shared sequencing layer is the essential next step in the modular blockchain roadmap. This mechanism unlocks the potential for a new class of secure, cross-chain DeFi primitives that rely on guaranteed atomic execution, such as decentralized cross-rollup exchanges and lending protocols. Future research will focus on optimizing the BFT-based consensus for greater throughput and exploring the use of threshold cryptography to achieve fair ordering by preventing the sequencer from seeing the transaction contents until a commit-time threshold is met.
Verdict
Decentralized shared sequencing is the foundational architectural primitive required to secure the modular blockchain ecosystem against systemic MEV and unlock trustless cross-rollup atomicity.
