Blind Synchronization of Channel Impulse Responses for Channel Reciprocitybased Key Generation Local, blind synchronization of Channel Impulse Responses for key generation algorithms without leaking details to adversaries is challenging, due to noise from transmission and measurements. Extracting the channel characteristics as a common source of randomness using CIR promises notable improvements in key bit rates for Physical Layer Security, however, reciprocity requirements necessitate successful synchronization at both ends.We propose a onedimensional Gaussian filter towards this end, which is simple, more robust, and outperforms competing approaches in almost all settings. To evaluate the quality of our approach, we assess the synchronization accuracy on extensive datasets. Experiments using data generated synthetically with the standardized IEEE 802.15 UWB channel model indicate a performance improvement of up to 31%. Performance on par or better than all alternatives in real measurements underlines its superior robustness against synchronization errors.

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.