Distributed Consensus Resilient to Both Crash Failures and Strategic Manipulations

In this paper, we study distributed consensus in synchronous systems subject to both unexpected crash failures and strategic manipulations by rational agents in the system. We adapt the concept of collusion-resistant Nash equilibrium to model protocols that are resilient to both crash failures and strategic manipulations of a group of colluding agents. For a system with $n$ distributed agents, we design a deterministic protocol that tolerates 2 colluding agents and a randomized protocol that tolerates $n - 1$ colluding agents, and both tolerate any number of failures. We also show that if colluders are allowed an extra communication round after each synchronous round, there is no protocol that can tolerate even 2 colluding agents and 1 crash failure.

💡 Research Summary

This paper explores distributed consensus in synchronous systems that are subject to both unexpected crash failures and strategic manipulations by rational agents within the system. The authors adapt the concept of collusion-resistant Nash equilibrium to model protocols resilient against both crash failures and strategic manipulations by a group of colluding agents. For a system with n distributed agents, they design a deterministic protocol that can tolerate up to two colluding agents and any number of failure nodes. Additionally, they propose a randomized protocol capable of tolerating up to n-1 colluding agents under the same conditions.

The paper highlights the importance of designing consensus protocols that not only handle traditional crash failures but also resist strategic manipulations by rational actors who may collude against the system’s integrity. The deterministic protocol is designed with a focus on robustness, ensuring that even if two agents are working together to disrupt the system, it can still achieve consensus reliably.

The randomized protocol takes a different approach, leveraging probabilistic methods to handle a larger number of potential colluders. This protocol ensures that as long as at least one agent remains non-colluding and operational, the system can still reach a consensus state despite significant manipulation attempts by other agents.

Furthermore, the paper proves that if colluding agents are allowed an extra communication round after each synchronous round, no protocol can tolerate even two colluding agents along with one crash failure. This finding underscores the critical role of timing and information dissemination in maintaining the integrity of distributed systems against both accidental failures and intentional disruptions.

The research contributes to the field by providing a rigorous framework for understanding how collusion-resistant Nash equilibrium can be applied to enhance the resilience of consensus protocols in complex, multi-agent environments. It offers valuable insights into designing more secure and reliable distributed systems that can withstand various forms of attacks and failures.