Censorship Resistance and Throughput with Multiple Concurrent Proposers

2026-07-18

AI Summary

This work addresses the vulnerability in blockchain systems where attackers can bribe a single block proposer to censor transactions. To mitigate this, the paper proposes a Multi-Concurrent Proposer (MCP) architecture that distributes block space among multiple proposers and introduces a transaction fee mechanism (TFM) incorporating penalties for duplicate submissions. The study formalizes economic censorship resistance (eCR) for the first time and develops an algorithm to compute mixed-strategy Nash equilibria under arbitrary TFMs. Through game-theoretic modeling, simulations, and validation on real Ethereum data, the experiments demonstrate that increasing the number of concurrent proposers significantly enhances eCR, while penalty-based TFMs effectively strengthen censorship resistance without compromising throughput.

Abstract

Censorship resistance is the defining advantage of blockchains over their centralized counterparts. Yet block proposers censor transactions for many reasons, from legal consequences to economic incentives. We study economically-incentivized censorship, modeled by an adversary who bribes proposers to exclude a target transaction, and define the economic censorship resistance (eCR) of a transaction as the adversary's expected cost of successful censorship divided by the user's expected payment for inclusion. Single-proposer systems are structurally weak by this measure: under a first-price auction the adversary need only match the user's bid, and fee burning pushes eCR to a few percent of what the user pays. We therefore turn to multiple concurrent proposers (MCP), where block capacity is divided among $n$ proposers and the block is the union of their sub-blocks. While MCP can substantially increase the cost of censorship by requiring the adversary to bribe many proposers, it also introduces transaction duplication, reducing throughput. The resulting trade-off depends critically on the transaction fee mechanism (TFM), which determines how fees are shared among competing proposers. We create a game theoretic model where validators construct blocks from a shared mempool, subject to an adversary's bribery attempt. We provide an algorithm that solves for the mixed equilibrium of a given mempool, which is characterized by the probability of including each transaction. This algorithm works for a wide class of TFMs, and allows us to calculate the expected throughput and censorship resistance for any bid distribution. We then use simulations to show how the eCR and throughput vary as the number of proposers increases. We compare three TFMs, finding that the duplication-penalizing TFM dominates the others across many settings. We also validate our findings with empirical Ethereum data.

Problem

• censorship resistance
• multiple concurrent proposers
• transaction fee mechanism
• throughput
• economic incentives

Innovation

• economic censorship resistance
• multiple concurrent proposers
• transaction fee mechanism
• game theoretic model
• throughput