Abstract
The chaos-based image cryptosystems have been widely investigated in recent years to provide real-time encryption and transmission. In this paper, a novel color image encryption algorithm by using coupled-map lattices (CML) and a fractional-order chaotic system is proposed to enhance the security and robustness of the encryption algorithms with a permutation-diffusion structure. To make the encryption procedure more confusing and complex, an image division-shuffling process is put forward, where the plain-image is first divided into four sub-images, and then the position of the pixels in the whole image is shuffled. In order to generate initial conditions and parameters of two chaotic systems, a 280-bit long external secret key is employed. The key space analysis, various statistical analysis, information entropy analysis, differential analysis and key sensitivity analysis are introduced to test the security of the new image encryption algorithm. The cryptosystem speed is analyzed and tested as well. Experimental results confirm that, in comparison to other image encryption schemes, the new algorithm has higher security and is fast for practical image encryption. Moreover, an extensive tolerance analysis of some common image processing operations such as noise adding, cropping, JPEG compression, rotation, brightening and darkening, has been performed on the proposed image encryption technique. Corresponding results reveal that the proposed image encryption method has good robustness against some image processing operations and geometric attacks.
Highlights
Widespread transmission of digital images over various communication media challenges to build credible security methods for the protection of confidential and sensitive information to be transmitted
Motivated by the above discussions, in this paper, we propose a new color image cryptosystem using coupled-map lattices (CML) and a fractional-order chaotic system
In order to demonstrate the robustness of the proposed image encryption scheme, we have performed some statistical tests on the histograms of the ciphered images and on the correlations of adjacent pixels in the ciphered image
Summary
Widespread transmission of digital images over various communication media challenges to build credible security methods for the protection of confidential and sensitive information to be transmitted. The cryptosystems based on widely used one-dimensional discrete chaotic maps suffer from fundamental drawbacks such as small key space, slow performance speed and weak security function [39] To overcome these limitations in the proposed encryption scheme, a 2D coupled map lattice (CML) and the fractional-order Chen chaotic system are utilized to generate the key streams. The fractional-order Chen chaotic system is employed to generate the key stream for diffusion, and the pixel values are modified sequentially to confuse the relationship between the cipher-image and the plain-image. The generation of pseudo-random numbers by the CML and the fractional-order Chen chaotic system and the division-shuffling process on the plainimage can be carried out simultaneously, i.e., in a parallel manner, which promotes the speed performance of the proposed image encryption algorithm. Our proposed scheme has higher security and overcomes the limitations in the image cryptosystem based on one-dimensional or two-dimensional chaotic maps
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