Implementation and Evaluation of Physical Layer Key Generation on SDR based LoRa Platform

TL;DR

This paper develops and evaluates a software-defined radio platform for physical layer key generation in LoRa networks, demonstrating high randomness and effective key creation using channel responses in indoor environments.

Contribution

It introduces a flexible SDR-based LoRa platform with a novel low-complexity preprocessing method for improved key generation from channel responses.

Findings

Achieved 367 high-randomness key bits from a single channel probe

Demonstrated effective key generation at 2 meters indoor distance

Utilized GNU Radio and USRP for flexible LoRa channel estimation

Abstract

Physical layer key generation technology which leverages channel randomness to generate secret keys has attracted extensive attentions in long range (LoRa)-based networks recently. We in this paper develop a software-defined radio (SDR) based LoRa communications platform using GNU Radio on universal software radio peripheral (USRP) to implement and evaluate typical physical layer key generation schemes. Thanks to the flexibility and configurability of GNU Radio to extract LoRa packets, we are able to obtain the fine-grained channel frequency response (CFR) through LoRa preamble based channel estimation for key generation. Besides, we propose a lowcomplexity preprocessing method to enhance the randomness of quantization while reducing the secret key disagreement ratio. The results indicate that we can achieve 367 key bits with a high level of randomness through just a single effective channel probing in an indoor environment at a distance of 2 meters under the circumstance of a spreading factor (SF) of 7, a preamble length of 8, a signal bandwidth of 250 kHz, and a sampling rate of 1 MHz.