Multiple Concurrent Proposers could triple blockchain censorship costs

A new arXiv paper from Aditya Saraf, Giannis Kaklamanis, Sarisht Wadhwa, and Fatima Elsheimy tackles a critical blockchain weakness: censorship resistance. The authors define economic censorship resistance (eCR) as the ratio of an adversary’s cost to successfully censor a transaction to the user’s payment for inclusion. They show that single-proposer systems are structurally weak – under a first-price auction, the adversary need only match the user’s bid, and fee burning drops eCR to a few percent.

The proposed solution is Multiple Concurrent Proposers (MCP), where block capacity is split among n proposers and the final block is the union of their sub-blocks. This forces an adversary to bribe many proposers, raising the cost of censorship significantly. However, MCP also introduces transaction duplication, reducing throughput. The trade-off depends critically on the transaction fee mechanism (TFM) used.

The researchers create a game-theoretic model where validators build blocks from a shared mempool under bribery attempts. They provide an algorithm to solve for the mixed equilibrium of any given mempool, calculating expected throughput and eCR for any bid distribution. They compare three TFMs using simulations and find that a duplication-penalizing TFM dominates across most settings. These findings are validated with empirical Ethereum data, offering a practical path to stronger censorship resistance without severe throughput loss.