Security enhancement of double-random phase encryption by iterative algorithm

We propose an approach to enhance the security of optical encryption based on double-random phase encryption in a 4f system. The phase key in the input plane of the 4f system is generated by the Yang-Gu algorithm to control the phase of the encrypted information in the output plane of the 4f system, until the phase in the output plane converges to a predesigned distribution. Only the amplitude of the encrypted information must be recorded as a ciphertext. The information, which needs to be transmitted, is greatly reduced. We can decrypt the ciphertext with the aid of the predesigned phase distribution and the phase key in the Fourier plane. Our approach can resist various attacks.