ARQ-Based Secret Key Sharing

TL;DR

This paper introduces a new secret key sharing method leveraging ARQ protocols and wireless multipath properties, enabling secure key distribution without prior channel knowledge and even against better eavesdroppers.

Contribution

It presents a novel ARQ-based framework for secret key sharing that does not require channel state information and distributes key bits across multiple frames for enhanced security.

Findings

Achieves positive secrecy rate despite better eavesdropper channels

Provides theoretical limits and practical implementations

Numerical results validate the approach

Abstract

This paper develops a novel framework for sharing secret keys using existing Automatic Repeat reQuest (ARQ) protocols. Our approach exploits the multi-path nature of the wireless environment to hide the key from passive eavesdroppers. The proposed framework does not assume the availability of any prior channel state information (CSI) and exploits only the one bit ACK/NACK feedback from the legitimate receiver. Compared with earlier approaches, the main innovation lies in the distribution of key bits among multiple ARQ frames. Interestingly, this idea allows for achieving a positive secrecy rate even when the eavesdropper experiences more favorable channel conditions, on average, than the legitimate receiver. In the sequel, we characterize the information theoretic limits of the proposed schemes, develop low complexity explicit implementations, and conclude with numerical results that validate our theoretical claims.