An Enhanced RSSI-based Secret Key Generation Framework for Secure Agricultural Edge-IoT Systems

Secure communication is essential for agricultural edge-IoT systems operating on resource-constrained wireless devices.Most RSSI-based secret key generation (SKG) methods improve only individual stages of the keygeneration pipeline and are rarely evaluated under realistic outdoor conditions.This paper presents HySKG, an endto-end RSSI-based SKG framework integrating parameter-tuned Moving Window Average preprocessing, Gray Code quantization, Cascade reconciliation, universal hash-based privacy amplification, statistical randomness evaluation, and AES-128 key extraction.The framework is implemented on Raspberry Pi 5 devices using IEEE 802.11n and evaluated across three outdoor propagation scenarios.HySKG achieves Pearson correlations of 0.937-0.993and a final Key Disagreement Rate of 0.00%, while retaining 3,072-3,328 bits of AES-compatible key material, corresponding to 24-26 AES-128 blocks, at an end-to-end Key Generation Rate of 25.99-26.66bps.The complete processing pipeline executes in less than 60 ms.Compared with five evaluated classical SKG baselines, HySKG produces approximately 3.7 times more retained key material under the same experimental conditions.NIST SP 800-22 testing indicates favorable statistical randomness characteristics for the evaluated key sequences, while the Leftover Hash Lemma analysis shows that the retained output lengths exceed the strict information-theoretic secrecy bounds.Therefore, the retained outputs are interpreted as statistically validated, AES-compatible key material rather than informationtheoretically secure secret keys.These results demonstrate the practical efficiency of the proposed integrated SKG framework for lightweight agricultural edge-IoT communication.