Design Of Image Divide-and-Conquer Compression Encryption System Based On Fractional-Order Chaos

With the increase in transmission speed,images have become a critical component of multimedia information and have received widespread attention.However,during the transmission process,images are susceptible to factors such as noise,interception,and tampering.To address these challenges,researchers need to continually innovate and improve information security technologies to ensure that multimedia data,such as images,are adequately protected.This helps maintain individual privacy rights,safeguard public interests,and promote social stability and prosperity.Image encryption is an effective means of solving these problems.However,existing chaos system encryption schemes often have a strong correlation between encryption time and image size.As the image size increases,the encryption time also increases proportionally.In practical application scenarios,not all cases require full-size image encryption and decryption.For example,in video cover images on video websites and pictures in cloud storage,users decide whether to execute the next operation by previewing the image.Therefore,constructing a divide-and-conquer encryption compression algorithm system is crucial.Such a system can quickly decrypt individual images for preview functionality and achieve a certain degree of compression,thereby saving storage space.Based on the aforementioned issues,this paper establishes a divide-and-conquer encryption algorithm system based on a four-dimensional fractional-order hyperchaotic Chen system.The main research contents and innovation points of this paper are as follows:1)A four-dimensional fractional-order hyperchaotic Chen system with high complexity is employed as the chaotic sequence for the divide-and-conquer compression encryption algorithm framework.The image encryption key is closely related to the plaintext image,including the hash value and a custom key value.These two factors fundamentally ensure the security performance of image encryption at the system’s basic level.2)This paper proposes a Value Difference Transformation(VDT),which divides the image into blocks and performs a positive transformation to reduce the number of pixel value bits and extract the key parts of the image.This includes separating the thumbnail and the primary and secondary subbands.The bit-reduced image can be losslessly compressed using DC coding,thereby saving storage space with a compression ratio of approximately 1.4.Meanwhile,the extracted thumbnail and subbands of varying importance can be used for divide-and-conquer encryption.On the basis of ensuring image security,independent encryption and decryption of the thumbnail are achieved to enable image preview functionality.Experimental results show that the encrypted thumbnail has excellent security performance and can resist various security attacks.3)To address the issue of lengthy DNA encryption,the Chinese Remainder Theorem(CRT)is introduced to solve the congruence equation system for adjacent pixels.Two pixel values are merged into one value,and then the important and less important parts are separated based on the number of high and low bits.Only the important parts undergo DNA encryption,followed by scrambling and diffusion across subbands.Finally,the encryption effect is dispersed globally through the combination of high and low bits and the CRT inverse transformation(INCRT).Both experimental results and security analysis demonstrate that this algorithm has excellent security performance and can resist various security attacks.4)By integrating the divide-and-conquer encryption algorithm framework with the Chinese Remainder Theorem encryption scheme,strong encryption based on the Chinese Remainder Theorem is performed on the thumbnail within the framework and applied to color images.A color image divide-and-conquer compression encryption system is built using Python backend and Web frontend technologies,making image compression and encryption more concrete and user-friendly.