Building Regular Registers with Rational Malicious Servers and Anonymous Clients -- Extended Version

TL;DR

This paper presents a protocol for emulating a regular register in a distributed system with anonymous clients and potentially rational malicious servers, using game theory to ensure correct behavior.

Contribution

It models the problem as a Bayesian game and designs a protocol that incentivizes rational malicious servers to behave correctly.

Findings

Existence of a Bayesian game equilibrium where servers behave correctly.

A protocol that enforces correct server behavior in the presence of rational malicious adversaries.

The protocol guarantees reliable register emulation despite server rationality and maliciousness.

Abstract

The paper addresses the problem of emulating a regular register in a synchronous distributed system where clients invoking ${\sf read}()$ and ${\sf write}()$ operations are anonymous while server processes maintaining the state of the register may be compromised by rational adversaries (i.e., a server might behave as \emph{rational malicious Byzantine} process). We first model our problem as a Bayesian game between a client and a rational malicious server where the equilibrium depends on the decisions of the malicious server (behave correctly and not be detected by clients vs returning a wrong register value to clients with the risk of being detected and then excluded by the computation). We prove such equilibrium exists and finally we design a protocol implementing the regular register that forces the rational malicious server to behave correctly.