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In a single substitution box, the same regions (pixels) of an image are encrypted to one unique symbol. To reduce this type of autocorrelation in data, chaos has been extensively applied over the last decade. By using chaotic maps, a single substitution box has been replaced with multiple substitution boxes for the encryption of autocorrelated data. The technique of multiple substitution boxes is becoming very popular among cryptographic algorithm designers to overcome the drawbacks of a single substitution box. In this paper, however, we found that replacing a single substitution box with multiple substitution boxes cannot provide a general solution for highly autocorrelated data. To address this issue, we propose a novel technique by adding chaotic diffusion to the existing substitution process. Extensive security analyses show that the proposed algorithm achieves both higher-level security and fast encryption time when compared with existing algorithms.

With the evolution of technologies, the size of an image data has been significantly increased. However, traditional image encryption schemes cannot handle the emerging problems in big data such as noise toleration and compression. In order to meet today's challenges, we propose a new image encryption scheme based on chaotic maps and orthogonal matrices. The main core of the proposed scheme is based on the interesting properties of an orthogonal matrix. To obtain a random orthogonal matrix via the Gram Schmidt algorithm, a well-known nonlinear chaotic map is used in the proposed scheme to diffuse pixels values of a plaintext image. In the process of blockwise random permutation, the logistic map is employed followed by the diffusion process. The experimental results and security analyses such as key space, differential and statistical attacks show that the proposed scheme is secure enough and robust against channel noise and JPEG compression. In addition to complete encryption for higher security, it also supports partial encryption for faster processing as well.

Due to easy and simple implementation, normally single 1-D chaotic maps like logistic and sine maps are employed in multimedia data encryption. However, data encrypted through a single chaotic map does not provide better security in terms of resistance against various attacks. In this paper, 2D Henon chaotic map and skew tent map are deployed in the design of an efficient chaos-based image encryption algorithm. To confuse the relationship between plaintext and ciphertext images, both chaotic maps play a key role in the permutation and diffusion mechanism. In the confusion stage, firstly, the Henon chaotic map generates two different chaotic sequences, which are further applied in row and column permutation of plaintext image. The pixel values diffusion is produced by unimodal skew tent map via XOR operations. In the last stage of encryption algorithm, Hussain's substitution box is used to substitute each pixel into a new random pixel. Extensive security analysis and resistance to statistical attack prove the security of anticipated scheme.

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