Optical multi-image encryption based on chaotic fingerprint phase mask and multi-slice diffractive imaging

To enhance the efficiency and security of optical encryption systems, we propose a novel optical multi-image encryption scheme based on chaotic fingerprint phase mask (CFPM) and multi-slice diffractive imaging in this paper. Multiple original images are initially arranged along the axial direction with a fixed interval between each image, forming a multi-slice object. Then, under the illumination of different speckle patterns, the multi-slice object is encrypted into a series of noise-like diffractive patterns using the CFPMs placed at different free-space propagation distances. The original images can be recovered by employing the iterative phase retrieval algorithm along with the correct decryption keys. Notably, the CFPMs are generated by the fingerprint and chaotic Henon map, which are only used as interim variables. The fingerprint and chaotic parameters are used directly as secret keys. This approach offers improved convenience for key storage and management. Moreover, fingerprints possess are inherently unique and have a strong connection to the user, significantly enhances the overall security of the encryption scheme. Additionally, the encryption scheme benefits from the additional security provided by the illumination pattern and the free-space propagation distance. Numerical simulation results demonstrate the high security of the proposed scheme.