Dynamic Chaotic Encryption Using Bit Division Multiplexing and Geometric Shaping

Optical wireless communication (OWC) techniques offer ultra-broad spectrum to mitigate the bandwidth-hungry in radio frequency for wireless connections. However, security risk is a critical issue that should receive significant attention. In this Letter, a dynamic chaotic encryption scheme is proposed for OWC systems to improve physical-layer security. In this scheme, the dynamic key is generated from the transmitted information, which is used to intercept the static chaotic sequence to encrypt the information at the two levels: bit and symbol. Further, bit division multiplexing in combination with geometric shaping is proposed to co-transmit the encrypted information and dynamic key, where the optimization objective is to minimize the bit-error ratio of the decrypted information. The effectiveness of the proposed dynamic chaotic encryption scheme is demonstrated via a 64-point constellation transmission, where each symbol carries 2-bit dynamic key and 4-bit encrypted information for transmission.