Several multimedia applications encounter difficulties due to concerns about the security of the underlying digital images. The peculiar properties of digital images, such as voluminous data, redundant data, and significant correlation between neighboring pixels, are typically strenuous to be handled by conventional encryption techniques. Further, several well-known image cryptosystems are flawed by different security issues, including fixed encryption parameters, inadequate plainimage sensitivity, independence of keystream generation from the plainimage, equivalent decryption keys, and a limited key space. Hence, this paper suggests an effective chaotic-based image cryptosystem to remedy these defects and accomplish the requirements of secured image exchange. The suggested scheme adopts the confusion-diffusion architecture which incorporates a new scrambling mapping and a novel substitution mapping. During the scrambling stage, the plainimage is first decomposed into four non-overlapping regions, and then the information of each region is mixed with the others by swapping operations through cross-interaction mapping. While in the diffusion stage, the shuffled pixels are masked by a strongly plainimage-related keystream, allowing each bit of the plainimage to influence the entire enciphered image. The suggested architecture employs several chaotic maps, including 1D logistic map, 2D logistic map and 4D hyper-chaos system, which boost the dynamic behavior of the cipher. Moreover, both stages are fully parameterized mappings that are wholly dependent on the plainimage data, including the pixel summation, histogram variance, and entropy features of the input image in addition to the previously substituted pixel. The inclusion of these features in computing all encryption parameters makes the corresponding keystreams for two images that differ by only one bit completely distinct. Specifically, the suggested cryptosystem does not directly employ the parameters or initial seeds of the chaos maps used as a secret key. Instead, an external secret key-based mechanism is suggested to produce these parameters, which employs several non-linear operations, resulting in a "butterfly effect" where a small input change affects subsequent keystream bits. As a result, it can achieve several advantages, such as key sensitivity support, security enhancement, dynamic encryption, resistance to attacks, efficiency, scalability, and flexibility, addressing chaotic system key distribution issues. While the suggested cryptosystem initially employs a static external key for all plainimages, both the generated scrambling sequence and the diffusion keystream are unique (representing a one-time key) to each image. Moreover, our architecture adjusts the external key used for each pixel based on the previously enciphered information. So, even a small change in the external key or input image results in completely different computed parameters. This creates a unique chaotic behavior that controls both the confusion and diffusion operations through different chaotic sequences. Consequently, the suggested cryptosystem can properly withstand different attacks involving the most potent known/chosen plainimage attack. Visually and computationally, the conducted experimental simulations attest that the suggested strategy delivers a superior security level and a noteworthy encryption quality compared to other techniques.
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