A novel chaos-based permutation for image encryption

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Image encryption is an essential method for ensuring confidentiality during transmission on open channels. Digital images have a high correlation with large redundant data, requiring alternative spatial handling during encryption. Digital chaos offers shared properties of randomness and sensitivity that can provide secure image encryption. The security and performance of chaotic image ciphers depend on the underlying digital chaotic map. Therefore, classical chaotic maps must improve security while maintaining implementation time. The main objective of this paper is to propose a new image encryption algorithm based on an enhanced chaotic map that offers high security and low time consumption. A new perturbed logistic chaotic map based on hybridizing backward and forward perturbation methods is introduced, which exhibits better chaotic features than other existing chaotic systems such as a large chaotic range, higher sensitivity, and randomness. Based on this, a new image encryption algorithm is proposed, employing a novel permutation operation and two substitution operations to achieve superior encryption speed and efficiency. The novel permutation operation based on a chaotic data sequence utilizes all chaotic states to generate 8-bit numbers. Each index of the resulting 8-bit number is compiled into one block. The plain image is then scanned in accordance with the randomized indices of each block. The two substitution operations involve an XORing operation for each pixel and a hashing process for each block. The newly proposed encryption algorithm can effectively encrypt images of varying sizes and types, transforming them into indecipherable cipher images that successfully pass through rigorous security tests, including differential attack analysis with a score of 28/28 and local Shannon entropy with a score of 25/28. The experimental findings showcase the superior performance of the proposed cipher over existing chaotic image ciphers, creating a cipher image that resembles noise and has the ability to resist a diverse range of cyber-attacks.