Digital image encryption and decryption algorithm based on wavelet transform and chaos system

During the transmission of digital image, in view of the security problem, use 2-D discrete wavelet transform and chaos system to realize the image encryption and decryption. When the target image is encrypted, firstly, the `bior3.7' wavelet is used for wavelet decomposition; and it can get the low and high frequency wavelet coefficients; then, the 1-D Logistic chaos sequence is used to reorder the low frequency wavelet coefficient matrix, the encrypted image can be obtained with inverse wavelet transform. The process of decryption is opposite with encryption, after decrypting the chaos sequence, the decrypted image can be obtained with wavelet reconstruction. The experiment results show that the encrypted image has high security, the decrypted image has small distortion and strong ability to resist noise attack; and the algorithm has good effectiveness and robustness.