JPEG彩色图像加密新算法

基于复合混沌和有限整数域上的仿射变换,提出一种结合彩色图像压缩编码的加密算法。先在空域对红、绿、蓝分量以8×8大小块为基本单元统一进行位置置乱,打乱分量之间的组合关系,接着进行正常的压缩。在量化系数之后,对所有的直流系数统一进行置乱、自适应地代换和扩散,对所有的交流系数统一进行置乱、自适应地改变符号位,其中置乱操作在改变系数位置的同时根据坐标混合它的值,自适应的操作通过利用中间数据扰动复合混沌系统来实现。算法密钥空间大,敏感性强,安全性高;构造的复合混沌系统形式简单,易于并行实现;得到的密文与直接压缩的图像大小相当。

Novel encryption for JPEG color image

On the basis of compound chaos and affine transformation in finite integer domain,a novel encryption algorithm is proposed,which is embedded in the compression process of color images.Firstly,it scrambles the blocks of 8×8pixels of red,green and blue components globally in space domain to disarrange the combination relationship among three components,and then proceeds with normal compression.Secondly,it scrambles,self-adaptively replaces and diffuses the frequency domain’s all direct current coefficients universally after quantization.Lastly,it scrambles alternating current coefficients’value and changes alternating current coefficients’signs self-adaptively.The scrambling function in it mixes coefficients’value according to corresponding coordination when changing coefficients’position,and the self-adaptive function is implemented by introducing image data in the process to disturb the chaos system.The algorithm has huge key space,strong sensitivity and high security.The constructed compoundchaos system,which has a brief form,can be realized parallel conveniently.The ciphertext has almost the same size as original image after direct compression.