Research On Image Chaotic Encryption And Hiding Algorithm In Discrete Wavelet Domain

The rapid development of Internet communications has facilitated the convenient and efficient delivery of information.However,the protection of information security has been greatly challenged in the same time.As one of the main carriers of information transmission,digital image is widely used in network multimedia.Therefore,how to ensure the secure interaction of digital image communication has become a research hotspot in academia.Because chaos has properties such as pseudo-random,ergodic,and sensitivity to initial values and system parameters which match the cryptography,and the discrete wavelet transform domain which provides more processing space for image encryption and concealment techniques,some researchers applied the chaos system together with the discrete wavelet transform to the image encryption and concealment system.So that the security of the encryption and concealment system is better protected.This thesis mainly introduces the principles of chaos theory,discrete wavelet transform and their application in image encryption and concealment technology.It focuses on the following two aspects of work:1.Thoroughly studied classical image chaos encryption and scrambling-diffusion encryption algorithms.For traditional chaotic encryption systems,the key space is small,the complexity of the sequence is insufficient,and the encryption system is single.Combining the advantages of large-scale key systems in high-dimensional chaotic systems and high robustness in discrete domain,a novel triple scrambling algorithm for RGB color image based on chaotic system is proposed.The improved algorithm first uses the Logistic chaotic sequence to scramble the RGB order of each pixel of the color image,and then one of the sequences generated from the four-dimensional Rabinovich hyperchaotic system is used to scramble the image pixel position by blocking processing.And the rest three of the sequences are used to scramble and diffuse the low frequency coefficients from the image discrete wavelet transform of each RGB channel.Finally,the encrypted image is obtained.This paper analyzes the results and performance of improved algorithms and reference algorithms.The actual experimental data shows that the proposed algorithm has effectively improved the security of image encryption.2.After learning and researching the existed discrete wavelet transform image hiding algorithms in the reference,it is found that the algorithm has a great influence on the loading map when it reaches the maximum hidden embedded amount,and its security is low.Therefore,an improved large-capacity color image hiding technology based on discrete wavelet transform is proposed.First,the secret image is initially encrypted using a chaotic encryption algorithm.Then discrete wavelet transform is performed on the image,and the appropriate embedding coefficient is selected according to the rules.Then,the encrypted secret image is embedded into the cover from the least significant bit of the selected discrete wavelet transform coefficient by bit operation(most embedded into the lower 4 significant bits)to obtain a dense image.The experimental results indicate the security and feasibility of the algorithm by using the index of each coefficient.Compared with the literature algorithm,the improved algorithm effectively improves the security of image hiding and the amount of data embedded in image hiding.