Color Image Encryption Using Spatial OAM Beam through a Multimode Fiber

Abstract

This paper proposes an optical color image encryption scheme to resist unsupervised machine learning attacks. The encryption system first encodes the pixel information of the plaintext color image using an orbital angular momentum (OAM) hologram while carrying RGB color information using the spatial degrees of freedom of vortex beam. Then, the information-encoded OAM beam is transmitted through a physically perturbed multimode optical fiber to generate the speckles as the encrypted ciphertext. Finally, the pre-trained Asymmetric Decoupling Deep Learning-based (ADDL) model takes the output speckles as input and successfully retrieves the grayscale value together with its corresponding color channel for decryption purposes. The proposed scheme uses spatial degrees of freedom to carry color information and achieves de-synchronized high-security color image encryption transmission. The system not only reconstructs high-fidelity images but also resists unsupervised machine learning attacks, ensuring enhanced security. Our work provides a promising path for further research on optical color image transmission and encryption with ultra-high security and crack resistance.