Introduction
More and more image information is conveying over network. The security of important images attracts a number of researchers to investigate image encryption algorithms [1–۱۰]. Chen et al. presented a new iterative phase retrieval algorithm for optical image encryption in three-dimensional space by considering the twodimensional plaintext as a series of particles distribution in 3D space [1]. Later, they proposed a new optical image encryption method based on multiple-region plaintext and phase retrieval algorithm in 3D space [2], where the plaintext was divided into multiple regions and each region was encrypted into one phaseonly mask. An optical image encryption scheme based on coherent diffractive imaging with multiple wavelengths was proposed [3]