Wiretap Channel With Causal State Information and Secure Rate-Limited Feedback

TL;DR

This paper investigates the secrecy capacity of a wiretap channel with causal state information and secure rate-limited feedback, providing bounds and capacity-achieving schemes under certain conditions.

Contribution

It introduces a new capacity bound for the wiretap channel with causal state info and feedback, and proposes a scheme combining wiretap coding with shared-key generation.

Findings

Secrecy capacity is bounded and tight when the legitimate channel is less noisy.

The capacity-achieving scheme combines Wyner wiretap coding with shared-key generation.

Feedback can be more effective for transmitting state information than for sending random keys.

Abstract

In this paper, we consider the secrecy capacity of a wiretap channel in the presence of causal state information and secure rate-limited feedback. In this scenario, the causal state information from the channel is available to both the legitimate transmitter and legitimate receiver. In addition, the legitimate receiver can send secure feedback to the transmitter at a limited rate Rf . We shown that the secrecy capacity is bounded. Moreover, when the channel to the legitimate receiver is less noisy than the channel to the eavesdropper, the bound is shown to be tight. The capacity achieving scheme is based on both the Wyner wiretap coding and two steps of shared-key generation: one from the state information and one via the noiseless feedback. Finally, we consider several special cases. When state information is available only at the legitimate receiver, the analysis suggests that unlike previous results involving feedback, it is better to use the feedback to send the state information to the transmitter (when possible), rather than send a random key.