Wiretap Channel with Causal State Information

TL;DR

This paper derives bounds on the secrecy capacity of wiretap channels with causal state information, showing the capacity can be increased compared to noncausal scenarios through key generation and advanced coding strategies.

Contribution

It establishes a new lower bound for the secrecy capacity with causal state information and compares it with the noncausal case, providing insights into capacity improvements.

Findings

Lower bound exceeds noncausal case capacity

Key generation from state information enhances secrecy rate

Bounds coincide for certain channel classes

Abstract

A lower bound on the secrecy capacity of the wiretap channel with state information available causally at both the encoder and decoder is established. The lower bound is shown to be strictly larger than that for the noncausal case by Liu and Chen. Achievability is proved using block Markov coding, Shannon strategy, and key generation from common state information. The state sequence available at the end of each block is used to generate a key, which is used to enhance the transmission rate of the confidential message in the following block. An upper bound on the secrecy capacity when the state is available noncausally at the encoder and decoder is established and is shown to coincide with the lower bound for several classes of wiretap channels with state.