# Protocol‐Agnostic Meta Key Distribution for Encrypted Wireless Communications Enabled by Space‐Time‐Coding Metasurface

## TL;DR

This paper introduces a secure key distribution system using programmable metasurfaces for encrypted wireless communication in indoor environments.

## Contribution

The novel MKD system uses metasurfaces to embed entropy in wireless channels for protocol-agnostic key generation.

## Key findings

- The MKD system achieves a key generation rate of 400 bit/s with a bit error rate below 3%.
- The system is resistant to passive eavesdropping and compatible with WiFi and Bluetooth.
- It supports applications in smart homes, IoT, and healthcare with minimal hardware changes.

## Abstract

Secure key distribution is fundamental to encrypted communications but remains challenging in indoor wireless scenarios due to high computational overhead and specialized hardware requirements. Here, a Meta Key Distribution (MKD) system based on programmable metasurface to securely distribute cryptographic keys and enable protocol‐independent encrypted communication is proposed. The metasurface embeds synchronized entropy into wireless channel by dynamically modulating the spatiotemporal properties of electromagnetic wave, thus allowing legitimate users to independently extract identical cryptographic keys. A prototype is implemented and experimentally validated in an indoor environment. The results show that the proposed MKD system achieves a key generation rate of 400 bit/s and a bit error rate below 3%, demonstrating reliable key generation performance and strong resistance to passive eavesdropping. In addition, the system can be readily integrated with standard wireless protocols such as WiFi and Bluetooth without requiring significant modifications to existing communication hardware. This metasurface‐assisted approach provides a lightweight, compatible, and secure key distribution solution, suitable for emerging applications in smart homes, the Internet of Things, and healthcare environments.

This paper presents a programmable metasurface‐based Meta Key Distribution (MKD) system for secure, protocol‐independent key exchange in indoor wireless settings. By embedding entropy into the wireless channel, it enables lightweight, compatible cryptographic key generation. Experiments confirm reliable key agreement, low error rates, and strong eavesdropping resistance, supporting applications like IoT and smart healthcare.