基于离散分数余弦变换的图像加密算法研究*

为了提高图像加密的效率和安全性，采用态函数线性组合法构造了一种离散分数余弦变换函数，利用其良好的正交性能及具有分数阶参数和周期参数的特点，提出了一种基于离散分数余弦变换的图像加密新方法。该加密算法采用了图像分块（图元）的方法。将图像分成大小不同的图元，使用离散分数余弦变换对每个图元分别进行行变换和列变换，从而完成对图像的加密。实验结果分析表明，该算法的加密效果、效率和抗穷举攻击能力是令人满意的。

Image encryption algorithm based on DFRCT

In order to improve the efficiency and security of image encryption,this paper constructed a new discrete fractional cosine transform(DFRCT) with arbitrary period by the method of linear combination, with its well orthogonal performance, the fractional and period parameters, and proposed a new image encryption algorithm based on discrete fractional cosine transform.It adopted the method of image block (image element) in the encryption algorithm. Divided original image into different sizes of image elements first, and then used the discrete fractional cosine transform to encrypt each image element by rows and by columns, the image encryption achieved at last. The analyzed results of the simulation show that the encryption algorithm effectiveness, efficiency and ability to resist brute-force attack are satisfactory.