A hybrid two-step attack on double-images nonlinear cryptosystem using phase truncation operation

In this paper, a hybrid two-step attack strategy is proposed to break the double-images nonlinear encryption system using phase truncation operation. The attack process is composed of two steps. First, an iterative algorithm is exploited to obtain an approximate value of the encoded image when the ciphertext and the encryption key are placed on the input plane and the output plane, respectively. Second, two approximate values of the original images are achieved by the use of decryption key, which is generated by another two encryption keys. Simulation results show that the proposed hybrid attack strategy can effectively attack the existing double-images nonlinear cryptosystem.