Classical Correlation in Quantum Dialogue

TL;DR

This paper reveals that classical communication in quantum dialogue protocols leaks half of the secret message, challenging their claimed quantum efficiency and highlighting a security flaw in these protocols.

Contribution

It identifies a critical security flaw in quantum dialogue protocols where classical communication leaks information, and demonstrates that their claimed quantum efficiency is unachievable.

Findings

Half of secret messages are leaked through classical channels.

Quantum efficiency claims are not achievable due to information leakage.

Classical communication compromises security in quantum dialogue protocols.

Abstract

Classical communications are used in the post-processing procedure of quantum key distribution. Since the security of quantum key distribution is based on the principles of quantum mechanics, intuitively the secret key can only be derived from the quantum states. We find that classical communications are incorrectly used in the so-called quantum dialogue type protocols. In these protocols, public communications are used to transmit secret messages. Our calculations show that half of Alice's and Bob's secret message is leaked through classical channel. By applying Holevo bound, we can see that the quantum efficiency claimed in the quantum dialogue type of protocols is not achievable.