Optical information hiding based on complex-amplitude ptychographic encoding and visual cryptography

We propose a novel optical information hiding system based on complex-amplitude ptychographic encoding and visual cryptography. The information to be hidden is a binary image. In the process of hiding, the binary image is firstly decomposed into two visual keys(one is amplitude, another one is phase) by visual cryptography, and then the two visual keys are synthesized into a complex-amplitude sample. Placing it in the optical path of the ptychography diffraction imaging, a series of overlapping diffraction patterns are collected as the ciphertext. Ciphertext is highly uncorrelated and indecipherable compared to the binary image, resulting in high security. During the extraction process, it is necessary to reconstruct the amplitude and phase of the complex-amplitude sample, that is, two visual keys. Then perform incoherent superposition and image processing on them to obtain a binary image, without complicated optical implementations and any additional computation, resulting in the convenience of extraction. In addition, the extended coding of visual cryptography also further improves the security of the system. Simulation results show that this system is easy to implement, has high security and robustness. •Modulating the two visual keys with SLMs into a complex-amplitude key.•The ciphertext has a great deal of resistance against GS algorithm extraction.•Visual cryptography and ptychography increases the diversity of system keys.•The system has high security.