# Breaking Through the Bottleneck of Wireless Physical-Layer Key Generation by Dynamic Agile Reconfigurable Intelligent Surface Antenna (DARISA)

## TL;DR

This paper introduces a new antenna system that improves wireless key generation rates in IoT environments.

## Contribution

The novel Dynamic Agile Reconfigurable Intelligent Surface Antenna (DARISA) addresses low key generation rates in quasi-static environments.

## Key findings

- DARISA mitigates slow channel variations and channel correlation by injecting two-sided randomness.
- The proposed method enhances key generation rates while resolving all three key issues in PLKG.
- Theoretical analysis and simulations confirm the superiority of DARISA in physical-layer key generation.

## Abstract

In widely deployed Internet of Things (IoT) scenarios, physical-layer key generation (PLKG) serves as a useful complement to conventional cryptographic methods, yet it often suffers from a fundamentally low key generation rate, which becomes particularly severe in quasi-static environments. This low rate is mainly attributed to three key issues: (1) slow channel variations, which provide insufficient randomness and thus limit the key generation rate; (2) correlation between the legitimate channel and the eavesdropping channel, which reduces the uniqueness of the extracted key and further degrades the achievable rate; and (3) insufficient degrees of freedom in the key source, which constrain the key space. To address these challenges, this paper introduces the Dynamic Agile Reconfigurable Intelligent Surface Antenna into physical-layer key generation. By deploying metasurface antennas at both ends and independently applying random phase modulation, the scheme injects two-sided randomness, thereby mitigating the adverse effects of quasi-static channels and legitimate eavesdropper channel correlation. Moreover, by leveraging the dynamic, agile, and reconfigurable characteristics of the metasurface antennas in the key generation process, the proposed approach can further enhance the key generation rate while simultaneously resolving all three issues above. The proposed scheme is developed under a general setting where correlation exists between the legitimate and eavesdropping channels. A closed-form expression for the key capacity is rigorously derived, accompanied by detailed theoretical analysis and simulations. The results demonstrate the superiority of the proposed approach when applied to physical-layer key generation.