Nonlinear optical cryptosystem free from amplitude-phase retrieval attacks

We present a new optical image encryption method using nonlinear cryptosystem to make it resistant against the amplitude phase retrieval algorithm. In order to enhance the security features, pixel scrambling is introduced into the image encryption process, in which cascaded two steps of phase-truncated Fourier-transform are used. In the proposed scheme, three phase only masks are used as the decryption keys with the scrambling key used for retrieving the input information. To measure the efficacy of the proposed nonlinear cryptosystem, mean square error is calculated for the decryption process.