基于加权直方图位混淆与分阶混沌异扩散的快速图像加密算法

目的为了解决当前图像加密技术因在置乱和扩散过程忽略了明文像素特性,导致其抗明文攻击能力较弱,并且整个像素扩散均采用相同的加密机制来实现,存在安全性不理想问题,文中设计基于加权直方图位混淆和分阶混沌异扩散的快速图像加密算法。方法该算法充分利用整个明文的像素值,将其嵌入到整个置乱与扩散阶段,且在扩散过程中,利用不同的加密函数对不同的像素进行扩散。首先,联合Logistic与Tent映射,利用非线性组合思想构建新的低维混沌系统,并分析其混沌性能;考虑输入明文的像素值,建立像素加权直方图,借助外部密钥,生成复合混沌系统的初值,通过迭代输出随机序列;再将明文的每个像素在位水平上进行扩展,利用离散化的随机序列在位水平上实现明文混淆;随后,将分数阶理论嵌入Logistic映射中,构建分阶Logistic混沌映射,利用像素的加权直方图对其迭代,输出混沌数组;对混淆密文的像素进行分类,结合混沌数组,设计异扩散模型,对三类像素进行不同的加密。结果测试结果显示,与当前混沌加密算法相比,所提加密机制具有更强的抗明文攻击能力,其输出密文的像素分布更为均匀。结论所提加密技术兼顾了较高的安全性与效率,能够较好地保护图像在网络中安全传输。

Fast Image Encryption Algorithm Based on Weighted Histogram Bit Confusion and Fractional Order Chaotic Diffusion

The work aims to design the fast image encryption algorithm based on weighted histogram bit confusion and fractional order chaotic diffusion, for the purpose of solving theses defects as low anti-plaint attack induced by ignoring the characteristics of plain pixels during the scrambling and diffusion, and low security caused by using the same encryption function during the whole pixel diffusion in current image encryption technology. The algorithm made full use of the pixel value of the entire plaintext, and embedded it into the whole scrambling and diffusion phase, and different encryption functions were used to diffuse different pixels in the diffusion process. Firstly, combined with Logistic and Tent map, a new low-dimension chaotic system was constructed by means of the nonlinear combination thought and its chaotic performances were analyzed. The pixel weighted histogram was established by taking into account the pixel value of the input plain, and the initial value of the composite chaotic system was generated by means of the external key. The random sequence was outputted by iteration. Then, each pixel of the plaintext was extended on the level of the plaintext, and the plaintext was confused by the discrete random sequence. Subsequently, the fractional order Logistic chaotic map was constructed by embedding fractional order theory into Logistic map, and the chaotic array was outputted to iterate it with the weighted histogram of the pixel. The different diffusion model was designed by classifying the pixels of the confusion cipher and combining the chaotic array to differently encrypt three kinds of pixels. The test results showed that the proposed encryption scheme had a stronger ability to resist plaintext attacks, and the pixels of output cipher was more uniform compared with the current chaotic encryption algorithm. With higher security and efficiency, the proposed encryption technology can better protect the images during their safe transmission in the network.