Boost+: Equitable, Incentive-Compatible Block Building

Block space on the blockchain is scarce and must be allocated efficiently through block building. However, Ethereum’s current block-building ecosystem, MEV-Boost, has become highly centralized due to integration, which distorts competition, reduces blockspace efficiency, and obscures MEV flow transparency. To guarantee equitability and economic efficiency in block building, we propose $\mathrm{Boost+}$, a system that decouples the process into collecting and ordering transactions, and ensures equal access to all collected transactions. The core of $\mathrm{Boost+}$ is the mechanism $\mathit{M}{\mathrm{Boost+}}$, built around a default algorithm. $\mathit{M}{\mathrm{Boost+}}$ aligns incentives for both searchers (intermediaries that generate or route transactions) and builders: Truthful bidding is a dominant strategy for all builders. For searchers, truthful reporting is dominant whenever the default algorithm dominates competing builders, and it remains dominant for all conflict-free transactions, even when builders may win. We further show that even if a searcher can technically integrate with a builder, non-integration combined with truthful bidding still dominates any deviation for conflict-free transactions. We also implement a concrete default algorithm informed by empirical analysis of real-world transactions and evaluate its efficacy using historical transaction data.

💡 Research Summary

The paper tackles the growing centralization and inefficiency of Ethereum’s current block‑building ecosystem, MEV‑Boost, which stems from the practice of “integration.” Integration occurs when a searcher sends its profitable transaction bundles exclusively to a single builder, giving that builder an unfair advantage in the MEV‑Boost auction. As a result, a few builders dominate block production, block‑space is under‑utilized because many non‑conflicting bundles are never combined, and off‑chain payments hide the true flow of MEV revenue.

To eliminate the incentive for integration while preserving economic efficiency, the authors propose Boost+, a new architecture that separates transaction collection from ordering and guarantees equal access to all collected transactions. The system runs inside a Trusted Execution Environment (TEE) and involves three actors: proposers, builders, and searchers. In each slot, Boost+ first gathers private order flows from users and searchers (including their bids) together with public mempool transactions. Simultaneously, builders submit their own block‑building algorithms.

The core of Boost+ is the mechanism M_{Boost+}, built on a Vickrey‑Clarke‑Groves (VCG) framework. The mechanism first executes a default algorithm that explores a fixed set of candidate blocks independent of any bids. Within this fixed set it efficiently identifies (a) the block that maximizes total reported value (the “winning block”) and (b) for each transaction, the counterfactual block that would have been chosen if that transaction’s bid were omitted. In the second stage, any builder‑submitted algorithms are also run, and the block with the highest total payment (default block or builder block) is selected. If a builder’s block wins, the surplus over the second‑highest block is refunded to the winning builder; the remaining value (winning payment minus refunds to searchers and builders) goes to the proposer.

Key incentive properties follow from this design:

• Builders: Truthful reporting of their block profit is a dominant strategy because the VCG payment exactly equals the externality they impose on others.
• Searchers: When the default algorithm dominates all builders, truthful bidding is also dominant. Moreover, for conflict‑free transactions (those whose reads/writes do not intersect with any other transaction), truthful bidding remains optimal even if a builder’s block wins.
• Integration deterrence: Even if a searcher could technically integrate with a builder, the strategy of not integrating and bidding truthfully dominates any joint deviation for conflict‑free order flows. Thus, the mechanism structurally removes the economic gain from exclusive integration.

The authors also present a concrete default algorithm derived from empirical analysis of real Ethereum blocks. Transactions are grouped by storage‑access conflicts; most blocks contain only small conflict groups, allowing exhaustive enumeration of feasible sub‑blocks within each group. Special cases such as sandwich attacks are handled with a single‑pass heuristic, and larger groups are trimmed to keep enumeration tractable. Evaluation on historical data shows that this algorithm constructs the optimal block in 53.2 % of cases and performs near‑optimally in the remainder, confirming its practicality.

Boost+ therefore achieves three major goals: (1) it restores fairness by giving every searcher’s bundle equal opportunity to be included; (2) it preserves economic efficiency by rewarding the block‑building algorithm that truly maximizes total value; and (3) it incentivizes innovation, as builders are compensated whenever their custom algorithms outperform the default. By running entirely within a TEE, Boost+ also protects the confidentiality of order flows and the integrity of the selection process. In sum, the paper delivers a rigorously analyzed, incentive‑compatible, and empirically validated solution to the centralization and opacity problems of the current MEV‑Boost paradigm.