Quantum data locking for high-rate private communication

TL;DR

This paper demonstrates that quantum data locking can enable private communication rates close to classical limits using symmetric quantum channels, with security guarantees under specific measurement constraints.

Contribution

It introduces a method to achieve near-optimal private communication rates via quantum data locking, highlighting security trade-offs and conditions for composability.

Findings

Private communication rate nearly equals classical capacity

Accessible information security is generally non-composable

Security is composable under finite-time measurement constraints

Abstract

We show that, if the accessible information is used as a security quantifier, quantum channels with a certain symmetry can convey private messages at a tremendously high rate, as high as less than one bit below the rate of non-private classical communication. This result is obtained by exploiting the quantum data locking effect. The price to pay to achieve such a high private communication rate is that accessible information security is in general not composable. However, composable security holds against an eavesdropper who is forced to measure her share of the quantum system within a finite time after she gets it.