Study And Implementation Of The Image Compression And Encryption Technology Based On Chaotic System

With the development of digital acquisition techniques, the informationamount carried by image is becoming larger and larger. Image security andbandwidth occupied in transmission are in urgent need of consideration. Aneffective way to slove this problem is to do image compression and encryption atthe same time.For the problems of low complexity and low security in low-dimensionalchaotic systems, by analyzing the existing methods of generating high-dimensionalchaotic system, this paper proposes a new design method to generatehigh-dimensional chaotic equation and analyzes the dynamical nature of the chaoticsystem under different parameters and selects the hyper-chaotic system for colorimage encryption. Through interleaving the different binary of different chaoticsequence to generate pseudo-random sequences, and reusing the pseudo-randomsequences in encryption can reduce the length of the chaotic sequence generated soas the time of the image encryption can be greatly reduced. According to theexisting scrambling and diffusion algorithms, this paper proposes a two-rounddiffusion algorithm based on the row-first diffusion and column-first diffusion,which can quickly eliminate the correlation of the pixels. Using the Cat map withparameters to scramble the image and making the parameters of Cat map relate tothe chaotic system and plain image will increase the difficulty of cracking cipherimage. By implementing the algorithm in Matlab, the result shows the proposedencryption algorithm has good encryption performance, high security, and fasterencryption speed.In order to ensure the security of image information, and to improve the imagetransmission rate, combining with the proposed image encryption algorithm basedon hyper-chaos, this paper uses the DCT dictionary to sparsely represent the colorimage as the main line, embeds encryption algorithm from three aspects in thecompression process to achieve image compression and encryption simultaneously.First, scrambles the location information of effective decomposition coefficients,which can eliminate the vulnerability that get the outline information of the imageand damage the relationship between pixels within the block of the image recovered with the wrong keys; Second, encrypts the sparse coefficients by controlling therepresentation of sparse coefficients with chaos; Third, encrypts the folded imagedata, and does not encrypt the data of information block that could ensure thesecurity of image data and guarantee the program could get a wrong image withwrong keys. Above three steps make the compression algorithm has a high security.Through experimental analysis, compression and encryption algorithm proposed inthis paper has a good performance in compression and security.By studying the encryption algorithm of colorful image and embedding it intothe image compression algorithm, to achieve image compression and encryptionsimultaneously, it can ensure the security and transmission rate of the image. Byanalyzing the results of the algorithm, the compression and encryption algorithmdesigned in this paper has a high security and good compression performance.