Perfectly Secure Message Transmission against Rational Adversaries

TL;DR

This paper introduces a game-theoretic model for secure message transmission, designing protocols resilient against rational adversaries who prefer undetected tampering, thus overcoming traditional cryptographic limitations.

Contribution

It develops new SMT protocols secure against rational adversaries, including scenarios with multiple non-cooperative adversaries and mixed malicious and rational threats.

Findings

Protocols secure against any rational adversary corrupting all but one channel

Circumvents cryptographic impossibility results using game theory

Addresses multi-adversary and mixed threat scenarios

Abstract

Secure Message Transmission (SMT) is a two-party cryptographic protocol by which the sender can securely and reliably transmit messages to the receiver using multiple channels. An adversary can corrupt a subset of the channels and commit eavesdropping and tampering attacks over the channels. In this work, we introduce a game-theoretic security model for SMT in which adversaries have some preferences for protocol execution. We define rational "timid" adversaries who prefer to violate security requirements but do not prefer the tampering to be detected. First, we consider the basic setting where a single adversary attacks the protocol. We construct perfect SMT protocols against any rational adversary corrupting all but one of the channels. Since minority corruption is required in the traditional setting, our results demonstrate a way of circumventing the cryptographic impossibility results by a game-theoretic approach. Next, we study the setting in which all the channels can be corrupted by multiple adversaries who do not cooperate. Since we cannot hope for any security if a single adversary corrupts all the channels or multiple adversaries cooperate maliciously, the scenario can arise from a game-theoretic model. We also study the scenario in which both malicious and rational adversaries exist.