Study On Image Encryption Algorithms Based On Chaos And Transform Domain

With the arrival of the era of internet and fast development of information technology, people are paying more and more attention on information security. The way to obtain information increasingly inclines to images and streaming media which makes image encryption become very popular. In this paper, image encryption based on chaos theory is studied, image encryption algorithms are realized and the performances of proposed encryption algorithms are analyzed. The specific work is that:(1) An image encryption improved method based on cat map and fractional Fourier transform is proposed. The original image is first multiplied by random phase generated by logistic map and sequently transformed by the fractional Fourier transform. Then the pixels of the transformed image are scrambled using two-dimensional cat map. The parameters of chaos function play an important role as keys in this proposed encryption method. Simulation results verify the feasibility of this encryption algorithm. Security analyses including key analysis, statistical analysis and robustness analysis are performed to show security and superiority of the proposed scheme.(2) A multiple-image encryption scheme based on three-dimension cat map and discrete quaternion Fourier transform (DQFT) is proposed. This method is used for four image encryption, four images are set as four parts of a quaternion and logistic map generates a4×4matrix to mix four images before using the DQFT on images and3D cat is also used to scramble each image. Simulation results demonstrate the feasibility and security analyses show superiority of the proposed scheme.