Digital image scrambling is to transform a digital image, to make it unrecognizable and become another chaos images without obvious meaning. If the operator knows the algorithms, he can reconstruct the original image from the chaos image by using the certain algorithms. Image scrambling encryption technology that based on Chaos Theory encrypts the image data stream through using the chaotic signal. It has the advantage like high security, encryption speed, large key space, and good scrambling effect. This paper studies the "extraordinary Key" and "to be trivial key" that are in the chaotic sequences that is caused by Logistic map, thus presents a image chaotic encryption algorithm that is based on hybrid chaotic sequence. Firstly, the algorithm generate hybrid chaotic sequence through the key; then through generates the corresponding offset matrix and permutation matrix the discrete mapping; finally, do the implementation of wavelet transform to the image, do the digital image scrambling encryption in the transform domain. In order to measure the degree of scrambling, we propose a "scrambling degree" concept. Experiments confirmed that the encryption algorithm has good scrambling in nature, and achieved good encryption effect. It confirmed the degree of scrambling encryption can effectively reflect the effect of scrambling encryption of the algorithm.
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