LoRa-PRIME: A Novel Secret Key Generation Framework Based on Periodic Bit Reversal and Modified Adaptive Quantization for Robust Cooperative Jamming LoRa Relay Networks

Abstract

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.