Covert chaotic encryption scheme based on compressive sensing in a W-band RoF system

This paper proposes a covert chaotic encryption (CCE) scheme based on compressive sensing (CS). The chaotic sequences used are generated by a six-dimensional hyper-chaotic D-system, where the <i>y</i> sequence is utilized for a chaotic index sparse block (CISB), the <i>x</i> sequence is used for generating the CS measurement matrix effectively, the <i>w</i>, <i>s</i>, and <i>u</i> sequences are employed for variable-parameter iterative Arnold transformations, and the <i>z</i> sequence is used for dual-random least significant bit (LSB) scrambling and embedding. The combination of these technologies enabled the scheme to achieve multi-domain, multi-dimensional, ultra-high-security encryption for multimedia image data. The scheme allows for the 4 Gb/s W-band orthogonal frequency division multiplexing (OFDM) signal transmission over 10 m in a radio-over-fiber (RoF) system. When the input optical power (IOP) exceeds 1 dBm, the bit error rate (BER) of the system is lower than the forward error correction (FEC) threshold of 3.8×10^-3. When the IOP is 6 dBm, the mean structural similarity index (MSSIM) between the decrypted and original image reaches 0.96, indicating good reconstruction quality. The key space reaches 10¹⁶⁰, effectively resisting various attacks. Compared to encryption schemes without CS, the transmission data volume is reduced by 75%. The combination of the CS and W-band RoF system demonstrates great potential for future high-capacity, high-security optical wireless transmission systems.