Secure and Robust Identification via Classical-Quantum Channels

TL;DR

This paper investigates the identification capacity of classical-quantum channels under uncertainty and privacy constraints, revealing conditions under which identification capacity equals transmission capacity and analyzing the impact of secrecy on capacity.

Contribution

It determines the identification capacity of compound and arbitrarily varying classical-quantum channels with privacy constraints, establishing key conditions for capacity equivalences and differences.

Findings

Identification capacity equals transmission capacity without privacy.

Secrecy capacity determines whether secrecy identification capacity is zero or equals transmission capacity.

Continuity and super-additivity properties of identification capacity are analyzed.

Abstract

We study the identification capacity of classical-quantum channels ("cq-channels"), under channel uncertainty and privacy constraints. To be precise, we consider first compound memoryless cq-channels and determine their identification capacity; then we add an eavesdropper, considering compound memoryless wiretap cqq-channels, and determine their secret identification capacity. In the first case (without privacy), we find the identification capacity always equal to the transmission capacity. In the second case, we find a dichotomy: either the secrecy capacity (also known as private capacity) of the channel is zero, and then also the secrecy identification capacity is zero, or the secrecy capacity is positive and then the secrecy identification capacity equals the transmission capacity of the main channel without the wiretapper. We perform the same analysis for the case of arbitrarily varying wiretap cqq-channels (cqq-AVWC), with analogous findings, and make several observations regarding the continuity and super-additivity of the identification capacity in the latter case.