Physical layer security enhancement scheme for PDM-16QAM system based on seven-dimensional CNN hyperchaotic encryption

The paper presents a secure communication scheme for the optical physical layer based on a seven-dimensional (7-D) Cellular Neural Network (CNN) hyperchaotic encryption. The encryption scheme utilizes a 7-D CNN hyperchaotic system to generate a hyperchaotic sequence as the key source. A portion of this key is selected to encrypt the plaintext image. The proposed scheme has been successfully implemented in a PDM-16QAM system with a data rate of 224 Gbps over a 200 km single-mode fiber (SMF). Experimental results show that authorized users can successfully decrypt the received signal, while eavesdroppers are unable to obtain useful information with a bit error rate (BER) of approximately 0.5. The key space of the scheme is 101792. Through key sensitivity analysis and key space analysis, it is known that the proposed encryption system can effectively resist various attacks by cryptanalysts. •A super large key space optical physical layer encryption scheme with a key space of 101792, which can effectively resist brute force attacks.•A seven-dimensional CNN hyper chaotic system and permutation encryption diffusion method are used for long-distance, high-speed optical physical layer encryption.•The optical physical layer encryption system can achieve a large key space at a lower complexity cost. And experiments have shown that it has good performance.