Image Encryption Algorithm Based On Contourlet And Physical Chaos Research

With the rapid development and application of the computer network technology andinformation processing technology, the multimedia information with the intuitive and richcharacteristics has gradually become an important way of information communication. However,the digital image is an important part of multimedia information, and occupies a decisive position.The advent of the information age brings fast and convenient information resources for people, andbrings how to solve the problem of information safety. However, the digital image compared withthe traditional text information has not only the large data and relatively high redundancy, but alsothe information encryption needs to spend a lot of time and resources, such the traditionallyclassical algorithm is hard to achieve the satisfactory effect in the digital image encryption.Therefore, we need to research the new algorithm to solve the problems existed in the imageencryption.The chaotic system with the characteristics of good pseudo random and the initial valuesensitivity is applied to the image encryption area. Contourlet transform with the characteristics ofgood multi-scale, localization and direction is applied to the digital image processing. This thesis isthe basis of introducing the current research situation of the digital image encryption, the basicknowledge of chaos theory and the principle of Contourlet transform, and presents an imageencryption algorithm based on Contourlet and physical chaos. The algorithm is that the spatialimage is encrypted after the Contourlet transform, and this is not only resolves the low efficiency ofthe spatial domain image encryption, but also adds encryption complexity. Physical chaos has thecharacteristics of stochastic-disturbing, and makes the mathematical operations with the Contourlettransform coefficients of original image, which causes the greater difficulties for illegal decryption.We do a lot of Matlab simulation experiments in this thesis. The results show that these algorithms can rapidly and effectively encrypt or decrypt image, and have the good confusion effect and thegood consistency between the decrypted image and the original image, at the same time,algorithms have the certain ability against destroying and noise. From the theoretical analysis topratice, lots of experiment results can reflect that image encryption algorithm based on Contourletand physical chaos presented in this thesis is safe and reliable.