Double-image Encryption Algorithms Based On Fractional Order Transform And Chaotic System

With the progress and the rapid development of modern science and technology,the transmission and the processing methods of image information have become more abundant.During the image transfer and processing,some attackers will try to steal important image information,which can easily cause the problem of important image information leakage,so it is very necessary to research the secure and efficient image encryption scheme.Chaotic system is widely used in the field of image encryption because of its own characteristics.The image encryption algorithms based on fractional order transform have large key space and strong robustness.To further improve the efficiency of image encryption,two double-image encryption algorithms are designed based on fractional order transform and chaotic systems.The specific research contents are as follows.A double-image encryption algorithm is proposed based on the phase-truncated multiple-parameter Fresnel transform.The pixel positions of the two plaintext images are scrambled and then the results are merged into one image.Subsequently,phase truncation and phase reservation are introduced in the multiple-parameter Fresnel transform domain to obtain the amplitude matrix and the phase matrix.The final encryption image is obtained with the pixel scrambling and XOR operations to modify the positions and the values of the amplitude matrix elements,where the chaotic sequences used in the pixel scrambling and XOR operations are produced by Logistic map,Logistic-Sine system and 2D Logistic-adjusted-Sine map.The image encryption scheme can resist the chosen-plaintext attack due to the nonlinear properties of XOR operation and phase truncation.The experiment results demonstrate the suggested double-image encryption strategy based on the phase-truncated multiple-parameter Fresnel transform has good performance.A double-image encryption scheme is designed by combining discrete fractional angular transform with fractional Fourier transform.The spectra can be obtained by performing the discrete cosine transform on the two grayscale images and then the spectra are compressed into an image with Zigzag scanning.Subsequently,the discrete fractional angular transform is carried out on the image and the result is processed with the double random phase encoding technique and the fractional Fourier transform.DNA sequence operation controlled by chaotic system is exploited to alter the pixel values to yield the ciphertext image.The statistical information of the plaintext images is used as the input of SHA-256 to calculate the initial condition of chaotic map,which further improves the security of the image encryption algorithm.The simulation results verify that the double-image encryption algorithm can effectively reduce the correlation between adjacent pixels of image and realize image encryption and decryption.