Secrecy in Cascade Networks

TL;DR

This paper analyzes how to incorporate secrecy into cascade networks using information-theoretic methods, balancing coordination performance with privacy against adversaries with side-information.

Contribution

It introduces bounds on performance and secrecy in cascade networks, providing a framework for optimal privacy-utility trade-offs with secret keys.

Findings

Derived tight inner and outer bounds on network performance with secrecy

Established the optimal equivocation as a special case

Provided examples demonstrating bound tightness

Abstract

We consider a cascade network where a sequence of nodes each send a message to their downstream neighbor to enable coordination, the first node having access to an information signal. An adversary also receives all of the communication as well as additional side-information. The performance of the system is measured by a payoff function evaluated on actions produced at each of the nodes, including the adversary. The challenge is to effectively use a secret key to infuse some level of privacy into the encoding, in order thwart the adversary's attempt to reduce the payoff. We obtain information-theoretic inner and outer bounds on performance, and give examples where they are tight. From these bounds, we also derive the optimal equivocation for this setting as a special case.