Digital Image Encryption by Combination of Fresnel Diffraction and Fourier Transformation

Based on the Fresnel diffraction theory and Fourier transformation principle, a method to fulfil the digital image encryption of a digital image by a combination of Fresnel diffraction and Fourier transformation is present. Two random phase masks are used in the encrypting process. In this paper an analytical expression is given to analyze the encrypting process of a digital image. A method for the decoding of the digital image through a Fresnel diffraction and a Fourier transformation process is also present. The two random phase variables and the distance of Fresnel diffraction can be regarded as keys for the encrypting of a digital image. Computer simulation for the encrypting and decoding is proved the correctness of the method.