Cooperative Secret Key Generation from Phase Estimation in Narrowband Fading Channels

TL;DR

This paper introduces a cooperative secret key generation protocol using phase estimation in narrowband fading channels, significantly improving key rates by leveraging relay nodes and analyzing estimation effects.

Contribution

It presents a novel cooperative protocol that enhances key generation rate in narrowband channels by incorporating relay-assisted phase estimation and theoretical bounds analysis.

Findings

Key rate improved by orders of magnitude.

Theoretical upper bounds established for secret key rate.

Simulation results confirm performance gains.

Abstract

By exploiting multipath fading channels as a source of common randomness, physical layer (PHY) based key generation protocols allow two terminals with correlated observations to generate secret keys with information-theoretical security. The state of the art, however, still suffers from major limitations, e.g., low key generation rate, lower entropy of key bits and a high reliance on node mobility. In this paper, a novel cooperative key generation protocol is developed to facilitate high-rate key generation in narrowband fading channels, where two keying nodes extract the phase randomness of the fading channel with the aid of relay node(s). For the first time, we explicitly consider the effect of estimation methods on the extraction of secret key bits from the underlying fading channels and focus on a popular statistical method--maximum likelihood estimation (MLE). The performance of the cooperative key generation scheme is extensively evaluated theoretically. We successfully establish both a theoretical upper bound on the maximum secret key rate from mutual information of correlated random sources and a more practical upper bound from Cramer-Rao bound (CRB) in estimation theory. Numerical examples and simulation studies are also presented to demonstrate the performance of the cooperative key generation system. The results show that the key rate can be improved by a couple of orders of magnitude compared to the existing approaches.