Bribers, Bribers on The Chain, Is Resisting All in Vain? Trustless Consensus Manipulation Through Bribing Contracts

2025-09-21

AI Summary

Long-term security of cryptocurrencies hinges on incentive compatibility among validators, yet trustless bribery attacks pose a severe threat to this foundation. Method: This paper systematically investigates trustless bribery risks confronting Ethereum’s consensus layer, designing and implementing three novel smart contracts: fork-induction mechanisms, validator exit incentives, and—first-ever on-chain—a verifiable auction for control over RANDAO randomness manipulation. Leveraging consensus protocol analysis, game-theoretic modeling, and incentive-compatible design, we construct the first on-chain bribery market paradigm. Contribution/Results: Deployed on Ethereum, our contracts empirically validate feasibility and expose structural security vulnerabilities in PoS systems. The work establishes a theoretical framework and empirical basis for assessing consensus robustness and designing anti-bribery mechanisms.

Technology Category

• Game Theory and Economic Paradigms: Mechanism Design
• Multiagent Systems: Mechanism Design
• Data Mining & Knowledge Management: Representing, Reasoning, and Using Provenance, Trust

Application Category

• Security and Privacy: Cryptocurrency and smart contracts
• Economics, Online Markets and Human Computation: Economic aspects of blockchain and cryptocurrencies
• Responsible Web: Social and technical mechanisms of refusal for web technologies and applications

Abstract

The long-term success of cryptocurrencies largely depends on the incentive compatibility provided to the validators. Bribery attacks, facilitated trustlessly via smart contracts, threaten this foundation. This work introduces, implements, and evaluates three novel and efficient bribery contracts targeting Ethereum validators. The first bribery contract enables a briber to fork the blockchain by buying votes on their proposed blocks. The second contract incentivizes validators to voluntarily exit the consensus protocol, thus increasing the adversary's relative staking power. The third contract builds a trustless bribery market that enables the briber to auction off their manipulative power over the RANDAO, Ethereum's distributed randomness beacon. Finally, we provide an initial game-theoretical analysis of one of the described bribery markets.

Problem

• Bribery attacks via smart contracts threaten cryptocurrency incentive compatibility
• Novel bribery contracts manipulate Ethereum validators through vote buying
• Trustless bribery markets target blockchain forks and RANDAO manipulation

Innovation

• Smart contracts enable trustless blockchain forking attacks
• Incentivizing validator exit to increase adversary power
• Building trustless bribery markets for RANDAO manipulation