An Image Encryption Method by Sub-image Shuffling, Bit-level Permutation and Diffusion using Chaotic Maps

Abstract

Transmission of images securely through a channel can be ensured using cryptography techniques. Encrypting an image with the help of chaotic maps provides security and authentication. This paper presents an image encryption method which consists of three main steps: Sub-image shuffling, bit-level permutation, and diffusion. The sub-image shuffling step is performed using a logistic map to increase the robustness of the proposed method. In the bit-level permutation process, highest four bits of each pixel are obtained. The bit-level row and column transformations are applied using the sequences generated by a chaotic tent map. Finally, in the diffusion step, the values of the image’s pixels are altered. Two different chaotic sequences which are obtained from the logistic map and tent map are employed. Five different parameters are selected as the secret keys for the encryption. The performance of the suggested method is tested with several analysis methods. Key space analysis shows that the proposed method can withstand brute force attacks. It is also proven that the method is highly sensitive to the secret keys. Histogram analysis illustrates the fact that the encrypted image’s pixels are uniformly distributed. Also, the correlation between the neighboring pixels is reduced in the encrypted image compared to the plain image. The differential analysis demonstrates that the method is sensitive to the slight changes in the plain image even though the same secret keys are used.