Single-Channel Color Image Encryption Algorithms With Chaos And Fractional Fourier Transform

With the improvements of living standard and technology, it is impossible for the simple text information to meet the human's demands of sensing the outer world and communications. Image, as an effective information carrier, is popular in our life and working. The important image information must be encrypted to counteract the evedropper's attacks in the open network environment. Image encryption is an active research focus in information security, although great progress has been achieved and much attention has been paid continuously. Chaotic encryption and encryption in transform domain are two important effective image encryption measures. Two new color image encryption algorithms are proposed by combining the chaotic function with the fractional Fourier transform (FrFT). The main jobs are as follows:A new color image encryption algorithm based on FrFT and chaos is proposed. The colors of the original color image are converted to HSI, and the S component is transformed by the random-phase encode based on FrFT, to obtain a random phase from its phase information. The H component as the first phase plate, combining with the random phase obtained from S component, I component is transformed by double random-phase encoding based on FrFT. Then chaos scrambling technology is used to encrypt the image, and color image encryption is implemented.A color image encryption algorithm based on cutting spectrum and 2D Arnold transform is proposed. The R, G and B color channels of the original color image are extracted, and their spectra are obtained separately by the frFTs, followed by cutting their spectra to combine a new spectrum. The combined spectrum is then scrambled by the 2D Arnold transform to improve the security. To enhance the sensitivity of the fractional order, random phase encoding is used to get the cipher image.One of the proposed single-channel color image encryption algorithms is implemented by neatly encoding in HSI color space, and the other is carried out by cutting spectrum. The proposed encryption system has features of low costs and simple structure since single-channel encryption algorithm does not need to encrypt three components of the color image in three channels separately. The effectiveness and the security of the proposed algorithms are analyzed with heavy simulations.