Cosine Transformed Chaos Function and Block Scrambling-Based Image Encryption

The authors propose an image encryption process based on chaos that uses block scrambling to reduce the correlation among the neighboring pixels and random order substitution for slightly changing the value of the pixel. The chaotic sequence for encrypting the image is generated by using two 3D logistic maps called enhanced logistic map and intertwining logistic map; the cos function helps in reducing linearity. The entire encryption process is composed of scrambling, image rotation, and random order substitution. Scrambling is used for permuting the pixels in the image so that we can reduce the correlation among the neighboring pixels, and this is followed by image rotation which can ensure that shuffling of pixels is done to the remaining pixels in the image, and at last the authors use random order substitution where they bring the small change in the pixel value. The proposed method has the capability of encrypting digital colored images into cipher form with high security, which allows only authorized ones who hold the correct secret key to decrypt the images back to original form.

Fourier–Mellin moment-based intertwining map for image encryption

In this paper, a robust image encryption technique that utilizes Fourier–Mellin moments and intertwining logistic map is proposed. Fourier–Mellin moment-based intertwining logistic map has been designed to overcome the issue of low sensitivity of an input image. Multi-objective Non-Dominated Sorting Genetic Algorithm (NSGA-II) based on Reinforcement Learning (MNSGA-RL) has been used to optimize the required parameters of intertwining logistic map. Fourier–Mellin moments are used to make the secret keys more secure. Thereafter, permutation and diffusion operations are carried out on input image using secret keys. The performance of proposed image encryption technique has been evaluated on five well-known benchmark images and also compared with seven well-known existing encryption techniques. The experimental results reveal that the proposed technique outperforms others in terms of entropy, correlation analysis, a unified average changing intensity and the number of changing pixel rate. The simulation results reveal that the proposed technique provides high level of security and robustness against various types of attacks.