Economic Censorship Games in Fraud Proofs

2025-02-27

AI Summary

This paper identifies a novel threat to fraud-proof mechanisms in optimistic rollups: attackers can bribe block proposers to economically censor defender transactions, thereby undermining the effectiveness of the challenge period. Method: We formally model this censorship game via three distinct game-theoretic frameworks, integrating Nash equilibrium analysis with consensus security guarantees to derive—analytically and explicitly—the minimal challenge period length required to ensure defender success as a function of protocol step count and adversarial/defensive budgets. Contribution/Results: We establish the first theoretical lower bound on the challenge period, revealing that the current standard of ~7 days is critically vulnerable under economic censorship. Our framework provides a verifiable methodology for configuring secure protocol parameters in censorship-resistant rollups and constitutes the first quantitative analysis of how economic censorship impacts fraud-proof security.

Technology Category

• Game Theory and Economic Paradigms: Mechanism Design
• Multiagent Systems: Mechanism Design
• Search and Optimization: Adversarial Search

Application Category

• Responsible Web: Measurement, analysis, and circumvention of Web censorship
• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems

Abstract

Optimistic rollups rely on fraud proofs -- interactive protocols executed on Ethereum to resolve conflicting claims about the rollup's state -- to scale Ethereum securely. To mitigate against potential censorship of protocol moves, fraud proofs grant participants a significant time window, known as the challenge period, to ensure their moves are processed on chain. Major optimistic rollups today set this period at roughly one week, mainly to guard against strong censorship that undermines Ethereum's own crypto-economic security. However, other forms of censorship are possible, and their implication on optimistic rollup security is not well understood. This paper considers economic censorship attacks, where an attacker censors the defender's transactions by bribing block proposers. At each step, the attacker can either censor the defender -- depleting the defender's time allowance at the cost of the bribe -- or allow the current transaction through while conserving funds for future censorship. We analyze three game theoretic models of these dynamics and determine the challenge period length required to ensure the defender's success, as a function of the number of required protocol moves and the players' available budgets.

Problem

• Analyze economic censorship in optimistic rollups
• Determine challenge period for defender success
• Model game theory of bribery censorship

Innovation

• Fraud proofs interactive protocols
• Economic censorship attack analysis
• Game theoretic models applied