基于组合混沌和位运算的图像加密算法

Image encryption algorithm based on combined chaos and bit operations

为了有效改进图像加密效果及其安全性,在对基于混沌系统及位运算的图像加密算法进行研究的基础上,提出基于组合混沌和位运算的图像加密算法,算法先对灰度图像进行位平面分解,考虑到图像的高四位含有较大的信息量,对高四位分别进行置乱变换,再与低四位构成一个整体进行置乱变换,然后组合置乱后的位平面,并与二值矩阵进行异或运算得到密文图像。实验结果表明,与像素位置置换算法和二维数据加密算法比较,改进算法具有更好的加密效率,密钥空间接近2192,具有较好的安全性,且能较好地抵御椒盐噪声和高斯噪声攻击,有效恢复出原始图像。

In order to effectively improve the image encryption effect and security ,according to the study on image encryption algorithm based on chaotic system and bit operations ,a image encryption algorithm based on combined chaotic system and bit operations was proposed . Firstly ,the original image was decomposed into bit-planes .Considering the massive contained information of the four high-planes of the image ,scrambling transformation was conducted on the four high-planes ,followed by scrambling transformation of combination with the four low high-planes .Then the encrypted image was obtained by conducting exclusive or (XOR) opera-tion between binary matrix and the combination of scrambled bit-planes .The experimental re-sult shows that compared with the pixel location permutation (PLP) algorithm and the en-hanced two-dimensional circulation encryption algorithm (TDCEA) ,the modified algorithm a-chieves a better encryption and the key space is near to 2192 .It has a better security and can be against the attack of salt-pepper noise and Gauss noise .It also can recover the original picture .