It Takes Two: A Peer-Prediction Solution for Blockchain Verifier's Dilemma

Abstract: The security of blockchain systems is fundamentally based on the decentralized consensus in which the majority of parties behave honestly, and the content verification process is essential to maintaining the robustness of blockchain systems. However, the phenomenon that a secure blockchain system with few or no cheaters could not provide sufficient incentive for (rational) verifiers to honestly perform the costly verification, referred to as the Verifier's Dilemma, could incentivize lazy reporting and undermine the fundamental security of blockchain systems. While existing works have attempted to insert deliberate errors to disincentivize lazy verification, the decentralized environment renders it impossible to judge the correctness of verification or detect malicious verifiers directly without additional layers of procedures, e.g., reputation systems or additional committee voting. In this paper, we initiate the research with the development of a Byzantine-robust peer prediction framework towards the design of one-phase Bayesian truthful mechanisms for the decentralized verification games among multiple verifiers, incentivizing all verifiers to perform honest verification without access to the ground truth even in the presence of noisy observations in the verification process. Furthermore, we optimize our mechanism to realize provable robustness against collusions and other malicious behavior from the verifiers, and also show its resilience to inaccurate priors and beliefs. With the theoretically guaranteed robust incentive properties of our mechanism, our study provides a framework of incentive design for decentralized verification protocols that enhances the security and robustness of the blockchain and potentially other decentralized systems.