Interleaved Group Quantization Algorithm for Key Extraction in Random Modulation Channel Sharing

Extracting characteristic information from atmospheric optical channels can be utilized to generate shared keys for communication parties. However, the autocorrelation of channel feature information within the correlation time caused by atmospheric turbulence limits the number of unrelated key bits that can be extracted per second. To address this issue, a shared key extraction scheme for random modulation channels is proposed. The scheme employs a controllable shared random source model with memory (CCRSM) to quantify the observed values of CCRSM to obtain keys. During the quantization phase, an interleave block quantization algorithm is employed. Initially, legitimate parties interleave and group the obtained CCRSM observations to eliminate the impact of temporal autocorrelation; subsequently, the processed CCRSM observations are quantified using a single-threshold method per group to obtain an initial bit sequence; finally, an encoding mapping operation is applied to generate the key sequence. This algorithm ensures that the keys extracted between legitimate communication parties have a low inconsistency rate and good randomness, and the key generation rate is significantly improved. Experimental results indicate that this scheme effectively reduces the key disagreement rate and enhances the key generation rate. Under a signal-to-noise ratio (SNR) of 30dB, the scheme achieves a key disagreement rate of 4.39×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> and a key generation rate of 2.99×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> bits per second, and the generated shared random keys pass the randomness tests of the National Institute of Standards and Technology (NIST).