Physical Layer Key Generation of LEO Satellite Communication Based on OTFS Technology

Low earth orbit (LEO) satellite signals cover extensive areas with high intensity, rendering them vulnerable to interception. However, the rapid movement of LEO satellites leads to severe Doppler frequency shift, making it extremely challenging to generate a consistent key using traditional physical key generation techniques. In response to these issues, we have fully utilized Orthogonal Time Frequency Space (OTFS) in dynamic environments and propose a physical layer key generation (PLKG) scheme based on delay- Doppler (DD) domain signal processing. In the preprocessing stage, we propose a Linearly Weighted Moving Average Coding (LW-MAC) algorithm that dynamically adjusts weights with varying channel response intensities, significantly reducing the inconsistency in channel estimation. Subsequently, to address the reduction in key security caused by insufficient key length, we propose a Maximum of Real and Imaginary parts of channel response Assisted Amplitude Quantization (MRIAAQ) algorithm, which increases the key length and enhances the key entropy value. Simulation results demonstrate that our proposed PLKG scheme has substantial advantages over bidirectional difference quantization (BDQ) and equal probability quantization schemes in terms of key disagreement rate (KDR). Moreover, our PLKG scheme significantly reduces the bit error rate (BER) by approximately 71.37% on average compared to artificial noise-aided physical layer security scheme, thereby greatly enhancing the security of dynamic satellite-to-ground communication.