Adjustable Security Scheme Based on Pseudo-Noise Key Distribution and Circular Domain Decision Optimization

In this paper, an adjustable security scheme based on pseudo-noise key distribution and circular domain decision optimization has been introduced. We employ chaotic mappings with adjustable dimensionality to generate keys, which are used to encrypt the orthogonal frequency division multiplexing (OFDM) signal. The pseudo-noise key allocation can mask the key information of the chaotic system as noise and transmit it concurrently with the encrypted signal. To enhance the transmission performance, we adopt a circular domain partitioning scheme to optimize the process of demodulation. Our strategy employs a soft-decision method in regions with higher decision difficulty, mitigating the shortcomings of limited precision in hard-decision method. For the symbols and pseudo-noise key with low decision difficulty, a hard decision strategy is adopted to avoid introducing high complexity. Transmission of a 27.72 Gb/s 16-quadrature amplitude modulation (16QAM) OFDM signal over a 2-km 7-core optical fiber is experimentally demonstrated. The results indicate that the proposed strategy, by optimizing the demodulation method for some received symbols, improved the receiver sensitivity by 0.75 dB at a bit error rate (BER) of 7.8 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup>. At the same time, while enhancing the flexibility of the encryption and demodulation modules, the encryption scheme can extend the cracking timescale to the order of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">108</sup> years.