Accountable Transaction Inclusion Lists: Enhancing Ethereum's Censorship Resistance

2026-07-24

AI Summary

This work addresses the threat posed by Ethereum block builders’ ability to conduct multi-block transaction censorship, which endangers time-sensitive applications and lacks effective accountability under current mechanisms. The paper proposes FairFIL (Fair Forward Inclusion List), the first accountable and verifiable censorship disclosure framework: builders must publicly disclose censored transactions, a committee verifies the completeness of these disclosures, and subsequent builders who fail to include the disclosed transactions forfeit their entire block reward. By anchoring disclosure policies, verification procedures, and incentive-compatible design directly into the protocol, FairFIL raises the long-term cost of censorship by an order of magnitude while preserving builders’ freedom to extract MEV. Empirical evaluation on Ethereum mainnet demonstrates that FairFIL substantially increases censorship costs, maintains mempool consistency sufficient for practical deployment, and provides strong compliance incentives for rational participants.

Abstract

In Ethereum, transaction inclusion is rarely in question; what matters is the delay until inclusion. Currently, block builders could exercise censorship across consecutive blocks, threatening time-critical applications, such as on-chain auctions. To mitigate this risk, existing proposals such as FOCIL, scheduled for deployment in late 2026, assign a committee to list transactions for mandatory inclusion. However, no committee member is held accountable for the actual inclusion of the transactions: an adversary can bribe the entire committee to omit any transaction for less than 2 Euro per block under current conditions. We argue that accountability, i.e., requiring all exclusion decisions to be publicly disclosed and verifiably complete, with violations attributable to a specific party, substantially raises censorship costs. To this end, we propose Fair Forward Inclusion Lists (FairFIL) as an accountable censorship resistance mechanism for Ethereum. In FairFIL, every builder must publish all transactions the builder chooses to censor, subject to a protocol-anchored policy; a committee verifies the completeness and validity of this disclosure. The subsequent builder must include these transactions, forfeiting the full block reward upon any omission. Therefore, under FairFIL, extending censorship beyond a single slot requires an assembler to forfeit a full block reward. We show that compliance is rational for all participants within our behavior model. Our empirical evaluation on Ethereum mainnet indicates that multi-block censorship costs one order of magnitude more than under existing proposals, while leaving the builder's MEV extraction freedom largely intact. Initial measurements further suggest that the mempool consistency FairFIL requires is met in practice.

Problem

• censorship resistance
• transaction inclusion
• accountability
• Ethereum
• block builder

Innovation

• accountability
• censorship resistance
• inclusion lists
• Ethereum
• MEV