# Steganography Protocols for Quantum Channels

## TL;DR

This paper explores quantum steganography protocols where two parties hide information within quantum channels, considering various cover and cypher tasks, and demonstrates improved methods under less restrictive assumptions.

## Contribution

It introduces new quantum steganography schemes for different cover and cypher task combinations, relaxing previous assumptions and enhancing security models.

## Key findings

- Quantum steganography protocols for classical and quantum cover tasks.
- Relaxed assumptions on shared keys and cover communication codes.
- Enhanced security and concealment in quantum channels.

## Abstract

We study several versions of a quantum steganography problem, in which two legitimate parties attempt to conceal a cypher in a quantum cover transmitted over a quantum channel without arising suspicion from a warden who intercepts the cover. In all our models, we assume that the warden has an inaccurate knowledge of the quantum channel and we formulate several variations of the steganography problem depending on the tasks used as the cover and the cypher task. In particular, when the cover task is classical communication, we show that the cypher task can be classical communication or entanglement sharing; when the cover task is entanglement sharing and the main channel is noiseless, we show that the cypher task can be randomness sharing; when the cover task is quantum communication and the main channel is noiseless, we show that the cypher task can be classical communication. In the latter case, our results improve earlier ones by relaxing the need for a shared key between the transmitter and the receiver and hold under milder assumptions on the cover quantum communication code.