Covert Quantum Communication

TL;DR

This paper demonstrates the feasibility of covert quantum communication over noisy optical channels, introduces protocols for covert quantum key distribution, and proposes a hybrid method for covert key regeneration using pseudorandom generators.

Contribution

It extends covert communication to the quantum domain, showing practical protocols for covert quantum key distribution and a hybrid key regeneration method.

Findings

Covert quantum communication is possible over noisy optical channels.

Positive key rates can be achieved while maintaining covertness.

A hybrid protocol for covert key regeneration using PRNGs and QKD is proposed.

Abstract

We extend covert communication to the quantum regime by showing that covert quantum communication is possible over optical channels with noise arising either from the environment or from the sender's lab. In particular, we show that sequences of qubits can be transmitted covertly by using both a single photon and a coherent state encoding. We study the possibility of performing covert quantum key distribution and show that positive key rates and covertness can be achieved simultaneously. Covert communication requires a secret key between sender and receiver, which raises the problem of how this key can be regenerated covertly. We show that covert QKD consumes more key than it can generate and propose instead a hybrid protocol for covert key regeneration that uses pseudorandom number generators (PRNGs) together with covert QKD to regenerate secret keys. The security of the new key is guaranteed by QKD while the security of the covert communication is at least as strong as the security of the PRNG.