基于时空混沌和小波变换的图像加密算法

本文提出一种基于时空混沌系统的图像加密算法。首先对明文图像进行Zigzag方式扫描置乱，再对置乱后的图像分块；然后用Logistic混沌系统生成的伪随机序列对其进行置乱，置乱结束后对其进行整数小波变换，利用基于耦合映像格子CML的混沌系统生成三个伪随机序列对低频小波系数进行置乱操作，同时对低频小波系数进行扩散，然后进行整数小波逆变换；最后再由基于CML的混沌系统生成两个伪随机序列对图像像素值进行扩散操作，得到最终的加密图像。经测试，该算法具有良好的加密性能，可以有效抵挡差分、明文等攻击。

An image encryption algorithm based on spatiotemporal chaos and wavelet transform

An image encryption algorithm based on spatiotemporal chaotic system is proposed. First, the plaintext image is scrambled by the Zigzag method. After the initial scrambled image is divided into blocks, the blocks are scrambled by the pseudo-random sequence generated by logistic chaotic system. Second, the integer wavelet transform is performed. Low-frequency wavelet coefficients are scrambled by three pseudo-random sequences produced by CML chaotic system. Meanwhile, the low-frequency wavelet coefficients are diffused. Then, the inverse integer wavelet transform is performed. Finally, the image is encrypted by using a pseudo-random sequence produced by CML chaotic system. The algorithm has good encryption performance. Encrypted images can effectively resist attacks such as difference and plaintext.