Private Semantic Communications with Separate Blind Encoders
Amirreza Zamani, Mikael Skoglund
TL;DR
This work addresses privacy-constrained semantic communication with two blind encoders, where encoder 1 designs a semantic $f(X)$ for a task $h(X)$ and encoder 2, possessing private data $S$, outputs a disclosed signal $U$ under a leakage budget $I(U;S)\\le\\epsilon$ to maximize $I(h(X);U)$. It formulates the privacy-utility objective $h_{\\epsilon}(P_{S,f(X)}) = \sup_{P_{U|S,f(X)}} I(f(X);U)$ subject to the leakage constraint and encoder design limits, and derives computable bounds using extended FRL and SFRL, including a common-information based tightness condition. The main contributions are explicit lower bounds $L_h^1(\\epsilon)$ and $L_h^2(\\epsilon)$ and an upper bound $h_{\\epsilon}(P_{S,f(X)}) \\le H(f(X)|S) + \\epsilon$, along with a bound on $I(U;h(X))$ that is independent of the semantic, and constructive privacy mechanisms. A MNIST-based numerical example illustrates the bounds, showing that the gap between upper and lower bounds can be small under realistic leakage and that the first lower bound often dominates, supporting practical applicability of the proposed framework.
Abstract
We study a semantic communication problem with a privacy constraint where an encoder consists of two separate parts, e.g., encoder 1 and encoder 2. The first encoder has access to information source $X=(X_1,\ldots,X_N)$ which is arbitrarily correlated with private data $S$. The private data is not accessible by encoder 1, however, the second encoder has access to it and the output of encoder 1. A user asks for a task $h(X)$ and the first encoder designs the semantic of the information source $f(X)$ to disclose. Due to the privacy constraints $f(X)$ can not be revealed directly to the user and the second encoder applies a statistical privacy mechanism to produce disclosed data $U$. Here, we assume that encoder 2 has no access to the task and the design of the disclosed data is based on the semantic and the private data. In this work, we propose a novel approach where $U$ is produced by solving a privacy-utility trade-off based on the semantic and the private data. We design $U$ utilizing different methods such as using extended versions of the Functional Representation Lemma and the Strong Functional Representation Lemma. We evaluate our design by computing the utility attained by the user. Finally, we study and compare the obtained bounds in a numerical example.
