# Private Broadcasting: an Index Coding Approach

## TL;DR

This paper explores privacy risks in index coding for broadcast channels, proposing metrics and encoding schemes to balance privacy of client requests and side information.

## Contribution

It introduces an information-theoretic privacy metric and designs encoding schemes with quantifiable privacy guarantees in index coding.

## Key findings

- Proposed a privacy metric for index coding.
- Designed encoding schemes achieving specific privacy levels.
- Identified a trade-off between request and side information privacy.

## Abstract

Using a broadcast channel to transmit clients' data requests may impose privacy risks. In this paper, we address such privacy concerns in the index coding framework. We show how a malicious client can infer some information about the requests and side information of other clients by learning the encoding matrix used by the server. We propose an information-theoretic metric to measure the level of privacy and show how encoding matrices can be designed to achieve specific privacy guarantees. We then consider a special scenario for which we design a transmission scheme and derive the achieved levels of privacy in closed-form. We also derive upper bounds and we compare them to the levels of privacy achieved by our scheme, highlighting that an inherent trade-off exists between protecting privacy of the request and of the side information of the clients.