Generalizing Multiple Access Wiretap and Wiretap II Channel Models: Achievable Rates and Cost of Strong Secrecy

TL;DR

This paper introduces new multiple access wiretap channel models with various wiretapping scenarios, deriving achievable strong secrecy rates and analyzing the secrecy cost associated with enhanced wiretapper capabilities.

Contribution

It generalizes existing models by incorporating stronger adversarial scenarios and derives achievable secrecy rate regions using novel information-theoretic techniques.

Findings

Achievable strong secrecy rate regions are established for all proposed models.

The models extend previous wiretap channel models to include more powerful wiretapper capabilities.

Secrecy costs are quantified in terms of achievable rates under different attack scenarios.

Abstract

In this paper, new two-user multiple access wiretap channel models are studied. First, the multiple access wiretap channel II with a discrete memoryless main channel, under three different wiretapping scenarios, is introduced. The wiretapper, as in the classical wiretap channel II model, chooses a fixed-length subset of the channel uses on which she obtains noise-free observations of one of the codewords, a superposition of the two codewords, or each of the two codewords. These thus extend the recently examined wiretap channel II with a noisy main channel to a multiple access setting with a variety of attack models for the wiretapper. Next, a new multiple access wiretap channel model, which further generalizes the multiple access wiretap channel II under the third wiretapping scenario, i.e., that which features the strongest adversarial model, is proposed. In this model, the wiretapper, besides choosing a subset of the channel uses to noiselessly observe the transmitted codeword symbols of both users, observes the remainder of the two codewords through a discrete memoryless multiple access channel. Achievable strong secrecy rate regions for all the proposed models are derived. Achievability is established by solving dual multi-terminal secret key agreement problems in the source model, and converting the solution to the original channel models using probability distribution approximation arguments. The derived achievable rate regions quantify the secrecy cost due to the additional capabilities of the wiretapper with respect to the previous multiple access wiretap models.