Quantum Byzantine Agreement via Hardy correlations and entanglement swapping

TL;DR

This paper introduces a device-independent quantum protocol for the Byzantine Generals problem that guarantees message integrity and detects cheating using Hardy correlations and entanglement swapping, without requiring classical message exchanges.

Contribution

It proposes a novel quantum scheme leveraging Hardy correlations and entanglement swapping for secure Byzantine agreement without classical communication.

Findings

Protocol is robust against bit-flipping errors.

Cheating by one party is detectable if messages are unambiguous.

No classical message exchange needed for security verification.

Abstract

We present a device-independent quantum scheme for the {\em Byzantine Generals} problem. The protocol is for three parties. Party $C$ is to send two identical one bit messages to parties $A$ and $B$. The receivers $A$ and $B$ may exchange two one bit messages informing the other party on the message received from $C$. A bit flipping error in one of the transmissions, does not allow the receiving parties to establish what was the message of $C$. Our quantum scheme has the feature that if the messages of the Byzantine protocol are readable (that is give an unambiguous bit value for any of the receivers), then any error by $C$ (cheating by one of the commanding general) is impossible. $A$ and $B$ do not have to exchange protocol messages to be sure of this.