No abstract

This paper introduces a new multi-image cryptosystem based on modified Henon map and nonlinear combination of chaotic seed maps. Based on the degree of correlation between the adjacent pixels of the plain image, a unique weight is assigned to the plain image. First, the coordinates of plain images are disrupted by modified Henon map as confusion phase. In the first step of diffusion phase, the pixels content of images are changed separately by XOR operation between confused images and matrices with suitable nonlinear combination of seed maps sequences. These combination of seed maps are selected depending on the weight of plain images as well as bifurcation properties of mentioned chaotic maps. After concatenating the matrices obtained from the first step of diffusion phase, the bitwise XOR operation is applied between newly developed matrix and the other produced matrix from the chaotic sequences of the Logistic-Tent-Sine hybrid system, as second step of diffusion phase. The encrypted image is obtained after applying shift and exchange operations. The results of the implementation using graphs and histograms show that the proposed scheme, compared to some existing methods, can effectively resist common attacks and can be used as a secure method for encrypting digital images.

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This paper introduces a new multi-image cryptosystem based on modified Henon map and nonlinear combination of chaotic seed maps. Based on the degree of correlation between the adjacent pixels of the plain image, a unique weight is assigned to the plain image. First, the coordinates of plain images are disrupted by modified Henon map as confusion phase. In the first step of diffusion phase, the pixels content of images are changed separately by XOR operation between confused images and matrices with suitable nonlinear combination of seed maps sequences. These combination of seed maps are selected depending on the weight of plain images as well as bifurcation properties of mentioned chaotic maps. After concatenating the matrices obtained from the first step of diffusion phase, the bitwise XOR operation is applied between newly developed matrix and the other produced matrix from the chaotic sequences of the Logistic-Tent-Sine hybrid system, as second step of diffusion phase. The encrypted image is obtained after applying shift and exchange operations. The results of the implementation using graphs and histograms show that the proposed scheme, compared to some existing methods, can effectively resist common attacks and can be used as a secure method for encrypting digital images.

This paper presents a new method for encrypting gray-scale digital images. The proposed method uses a combination of the residue number system and chaotic maps to avoid the complexities of high-dimensional chaotic maps and improve the security of encryption and processing speed. In this method, the image pixel coordinates confusion operation is performed by Arnold's cat map, and the pixel content diffusion step is performed in two phases. In the first phase, the contents of the image pixels are converted to the introduced {(r-1)a, rb, (r + 1)c} residue number system and stored in a matrix. At the same time, a chaotic system produces a combination of Sinusoidal and Logistic maps of chaotic sequences, and after quantization, they are converted into the introduced residue number system and stored in another matrix of the same size. In the second phase of diffusion, XOR operation is performed between these two matrices. The implementation results show that the use of the residue number system, in addition to improving the evaluation parameters, improves the processing time, and the average processing time for encryption is 0.15 seconds. Also, the uniform histogram, the entropy of about 8, and the correlation coefficient close to 0 of the encrypted images all demonstrate the high security of the proposed method.