Distributed Physical Layer Key Generation for Secure LPWAN Communication LowPower Wide Area Networks (LPWAN) has emerged as the dominant open specification in recent years due to its ability to offer affordable connectivity to the lowpower devices distributed over large geographical areas. However, security issues have not been fully addressed in LPWAN specifications, especially, key distribution and key management. Physical layer key generation, which exploits wireless channel reciprocity and randomness to generate secure keys, has attracted considerable attention in recent years. In this paper, we exploit the physical layer key generation problem in LPWAN communication and present a distributed and lightweight key generation scheme for Long Range (LoRa) based network. It explores the shared randomness extracted from measured RSSI (Received Signal Strength Indicator) as consensus information to generate secure keys. To negotiate the RSSI signal as a bidirectional consistent key sequence, we propose a novel levelcrossing quantization algorithm with an improved Cascade key agreement protocol to improve the key generation rate, as well as to avoid information leakage during transmission. We implement the proposed physical layer key generation scheme in a LoRa network prototype. Then we conduct extensive experiments in stationary and mobile indoor environments to evaluate the efficiency of the proposed key generation scheme. Experimental results show that its achievable key rate can reach 29.5% in stationary scenario and 35.5% in mobile scenario. Its key generation rate can exceed 1 bits with a lightweight implementation on the LoRa network prototype. For the 128bit key sequence, it passes the the NIST suite of statistical tests.

LoRaBased Physical Layer Key Generation for Secure V2VV2I Communications In recent years, VehicletoVehicle (V2V) and VehicletoInfrastructure (V2I) communication brings more and more attention from industry (e.g., Google and Uber) and government (e.g., United States Department of Transportation). These VehicletoEverything (V2X) technologies are widely adopted in future autonomous vehicles. However, security issues have not been fully addressed in V2V and V2I systems, especially in key distribution and key management. The physical layer key generation, which exploits wireless channel reciprocity and randomness to generate secure keys, provides a feasible solution for secure V2VV2I communication. It is lightweight, flexible, and dynamic. In this paper, the physical layer key generation is brought to the V2I and V2V scenarios. A LoRabased physical key generation scheme is designed for securing V2VV2I communications. The communication is based on Long Range (LoRa) protocol, which is able to measure Received Signal Strength Indicator (RSSI) in longdistance as consensus information to generate secure keys. The multibit quantization algorithm, with an improved Cascade key agreement protocol, generates secure binary bit keys. The proposed schemes improved the key generation rate, as well as to avoid information leakage during transmission. The proposed physical layer key generation scheme was implemented in a V2VV2I network system prototype. The extensive experiments in V2I and V2V environments evaluate the efficiency of the proposed key generation scheme. The experiments in real outdoor environments have been conducted. Its key generation rate could exceed 10 bits on our V2VV2I network system prototype and achieve 20 bits in some of our experiments. For binary key sequences, all of them pass the suite of statistical tests from National Institute of Standards and Technology (NIST).