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

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.