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IEEE Internet of Things Journal

FineLorKey: An Efficient LoRa Physical-Layer Key Generation Scheme Utilizing Fine-Grained Channel Impulse Response

Jiangtao Wang, Aiqun Hu, Yanbing Chen, Bingshu Dong, Shichen Sun

Published Dec 24, 2025• 2 citations
Publisher

Abstract

Physical layer key generation has emerged as a promising solution to secure communications in LoRa networks. However, existing LoRa-based key generation systems suffer from low efficiency and limited security due to their reliance on coarse-grained channel measurements. To overcome the limitation, this paper proposes FineLorKey, the first systematic physical layer key generation framework for LoRa that leverages fine-grained Channel Impulse Response (CIR). FineLorKey introduces a novel CIR extraction method tailored to LoRa Chirp Spread Spectrum (CSS) modulation. This method can be seamlessly integrated into the demodulation process without incurring additional computational overhead. Theoretical analysis demonstrates that the extracted CIR maintains high reliability under the low signal-to-noise ratio (SNR) conditions typical of LoRa environments. Furthermore, to address the dynamic SNR variations inherent in LoRa scenarios, this paper designs an SNR aware quantization scheme based on quantitative bit error rate analysis. The scheme dynamically adjusts the quantization order to maximize entropy extraction. Extensive experiments were conducted in diverse scenarios, including indoor and outdoor environments, line-of-sight and non-line-of-sight conditions, as well as both static and mobile settings. The results show that compared with RSSI-based methods, FineLorKey achieves a more than 10× improvement in key generation rate, reduces the key disagreement rate to below 5%, decreases channel information eavesdropping rate by over 60%, and exhibits strong robustness under large-scale deployment scenarios. These findings underscore the effectiveness and security of FineLorKey and mark a substantial advancement in wireless key generation for long-range, low-SNR wireless environments.

DOI
10.1109/jiot.2025.3648010

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Physical-layer security (PLS) schemes use the randomness of the channel parameters, namely, channel state information (CSI) and received signal strength indicator (RSSI) to generate the secret keys. There has been limited work in PLS schemes in long-range (LoRa) wide-area networks (LoRaWANs) which hinder their widespread application. Limitations observed in existing studies include the requirement of high correlation between channel parameter measurements for secret key generation in the proposed schemes and the evaluation of the schemes has only been done in either fully indoor or outdoor environments. The real-world wireless sensor networks (WSNs) and LoRa use cases might not meet both requirements thus making the current PLS schemes inappropriate for these systems. By considering the limitations found in existing PLS schemes, this article proposes LoRA-LiSK, a practical and efficient shared secret key generation scheme for LoRa networks. Our proposed LoRa-LiSK scheme consists of several preprocessing techniques (timestamp matching, two sample Kolmogorov–Smirnov tests, and a Savitzky–Golay filter), multilevel quantization, information reconciliation using Bose–Chaudhuri–Hocquenghem (BCH) codes, and finally, privacy amplification using secure hash algorithm SHA-2. The LoRa-LiSK scheme is extensively evaluated on real WSN/IoT devices in practical application scenarios: 1) indoor to outdoor and 2) LoRa static and mobile outdoor links. It outperforms existing schemes by generating keys with channel parameter measurements of low correlation values (0.2–0.6), while still essentially achieving high key generation rates, and low key disagreement rates (10%–20%). The scheme updates a key in approximately 1 h using an application profile with high transmission rate compared to 3 h reported by existing works while still respecting the duty cycle regulation. It also incurs less communication overhead compared to the existing works.
Physical-layer key generation is promising in establishing a pair of cryptographic keys for emerging LoRa networks. However, existing key generation systems may perform poorly since the channel reciprocity is critically impaired due to low data rate and long range in LoRa networks. To bridge this gap, this paper proposes a novel key generation system for LoRa networks, named ChirpKey. We reveal that the underlying limitations are coarse-grained channel measurement and inefficient quantization process. To enable fine-grained channel information, we propose a novel LoRa-specific channel measurement method that essentially analyzes the chirp-level changes in LoRa packets. Additionally, we propose a LoRa channel state estimation algorithm to eliminate the effect of asynchronous channel sampling. Instead of using quantization process, we propose a novel perturbed compressed sensing based key delivery method to achieve a high level of robustness and security. Evaluation in different real-world environments shows that ChirpKey improves the key matching rate by 11.03–26.58% and key generation rate by 27–49× compared with the state-of-the-arts. Security analysis demonstrates that ChirpKey is secure against several common attacks. Moreover, we implement a ChirpKey prototype and demonstrate that it can be executed in 0.2 s.
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 low-complexity 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.
Physical layer key generation that exploits reciprocity and randomness of wireless fading channels has attracted considerable attention in recent years. Despite much research efforts in this field, the problem of wireless key generation at long distance and low data rate remains unknown and has not been studied. In this paper, we conduct extensive experiments and analysis in real indoor and outdoor environments to explore the feasibility of wireless key generation for long range (LoRa)-based network. Our experimental results show that: 1) the low transmission rate will lead to low channel reciprocity which makes wireless key generation significantly challenging and 2) when the requirement of high reciprocity is fulfilled, two nodes can generate the same secret key even when they are far away from each other (a few kilometers). Building on the strengths of existing secret key extraction approaches, we present LoRa-Key, the first complete key establishment protocol for LoRa network by exploring the shared randomness extracted from measured received signal strength indicator. LoRa-Key employs a number of signal processing techniques to improve key generation rate significantly. Moreover, we propose a novel compressive sensing-based reconciliation framework to reduce mismatch rate. Experimental results show that LoRa-Key can achieve key establishment rates of 18 bit/s in stationary scenario and 31 bit/s in mobile scenario. To the best of our knowledge, this is the first work that studies key generation protocol for LoRa network.
Low-Power Wide Area Networks (LPWAN) has emerged as the dominant open specification in recent years due to its ability to offer affordable connectivity to the low-power 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 level-crossing 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 bit/s with a lightweight implementation on the LoRa network prototype. For the 128-bit key sequence, it passes the the NIST suite of statistical tests.
Physical-layer secret key generation (SKG) offers a lightweight security approach for resource-constrained Internet of Things (IoT) devices. However, most existing methods are designed for direct links and do not explicitly address relay-assisted LoRa networks. This paper presents LoRa-PRIME, an SKG framework that combines channel probing, Savitzky–Golay preprocessing, modified Adaptive Dual-Threshold Quantization (ADQ), Bose–Chaudhuri–Hocquenghem (BCH) reconciliation, Periodic Reversal for Keying (PRK) randomness enhancement, and SHA-256 privacy amplification. Experiments were conducted using real LoRa devices under indoor line-of-sight (LOS), indoor non-LOS, and outdoor non-LOS conditions. Savitzky–Golay filtering increased channel correlation (e.g., from 0.7595 to 0.8443 in indoor LOS), supporting reliable key extraction. The 4-bit modified ADQ achieved higher key agreement rates (up to 0.9745) and key generation rates (up to 33.04 bps) compared with Sky-Glow, while reducing key generation time to 7.75 s/key. PRK improved randomness quality, increasing the number of NIST-compliant keys from 4 to 14 in indoor LOS and showing similar improvements in other environments. Complexity analysis indicates approximately linear O(N)scalability, with more than 85% of execution time dominated by channel probing, while signal processing and cryptographic stages introduce minimal overhead. The measured energy consumption is 6.619 J per key, lower than several reported LoRa-based SKG implementations. These results suggest that LoRa-PRIME provides an efficient and practical SKG solution for relay-assisted LoRa IoT deployments.