Covert Communication and Key Generation Over Quantum State-Dependent Channels

TL;DR

This paper investigates the possibility of covert communication and secret key generation over quantum state-dependent channels, achieving positive rates and extending classical results to the quantum domain.

Contribution

It introduces the first positive-rate covert secret key generation scheme over quantum channels, generalizing classical results and establishing optimality in certain classical scenarios.

Findings

Achieved positive covert secret key rates over quantum channels.

Extended classical covert communication results to quantum state-dependent channels.

Demonstrated optimality in classical channel cases with non-causal state information.

Abstract

We study covert communication and covert secret key generation with positive rates over quantum state-dependent channels. Specifically, we consider fully quantum state-dependent channels when the transmitter shares an entangled state with the channel. We study this problem setting under two security metrics. For the first security metric, the transmitter aims to communicate covertly with the receiver while simultaneously generating a covert secret key, and for the second security metric, the transmitter aims to transmit a secure message covertly and generate a covert secret key with the receiver simultaneously. Our main results include one-shot and asymptotic achievable positive covert-secret key rate pairs for both security metrics. Our results recover as a special case the best-known results for covert communication over state-dependent classical channels. To the best of our knowledge, our results are the first instance of achieving a positive rate for covert secret key generation and the first instance of achieving a positive covert rate over a quantum channel. Additionally, we show that our results are optimal when the channel is classical and the state is available non-causally at both the transmitter and the receiver.