# Lightweight authentication for quantum key distribution

## TL;DR

This paper introduces a lightweight, secure authentication protocol for quantum key distribution that minimizes key consumption, using a ping-pong scheme and key recycling techniques to enhance efficiency and security.

## Contribution

It presents a novel authentication scheme for QKD based on a ping-pong method, reducing key consumption to below 1% with unconditionally secure key recycling.

## Key findings

- Authentication key consumption is below 1% in real scenarios.
- The protocol uses universal hashing and OTP encryption for security.
- Security is proven within a universally composable framework.

## Abstract

Quantum key distribution (QKD) enables unconditionally secure communication between distinct parties using a quantum channel and an authentic public channel. Reducing the portion of quantum-generated secret keys, that is consumed during the authentication procedure, is of significant importance for improving the performance of QKD systems. In the present work, we develop a lightweight authentication protocol for QKD based on a `ping-pong' scheme of authenticity check for QKD. An important feature of this scheme is that the only one authentication tag is generated and transmitted during each of the QKD post-processing rounds. For the tag generation purpose, we design an unconditionally secure procedure based on the concept of key recycling. The procedure is based on the combination of almost universal$_2$ polynomial hashing, XOR universal$_2$ Toeplitz hashing, and one-time pad (OTP) encryption. We demonstrate how to minimize both the length of the recycled key and the size of the authentication key, that is required for OTP encryption. As a result, in real case scenarios, the portion of quantum-generated secret keys that is consumed for the authentication purposes is below 1\%. Finally, we provide a security analysis of the full quantum key growing process in the framework of universally composable security.