基于改进型Henon映射的快速图像加密算法

为了解决传统Henon映射在密码系统中实现时混沌空间小和安全性低的缺陷，设计了一种改进型Henon映射。通过分岔图、混沌轨道、Lyapunov指数和近似熵分析表明改进型的Henon映射具有更大的混沌空间、更好的遍历性和更高的混沌复杂度，使其更加适用于设计安全的密码系统。基于改进型的Henon映射，提出了一种快速图像加密算法，该算法由多级块置乱和双向块扩散过程构成。在多级块置乱过程，明文图像被分成几个大小不等的图像块，然后对图像块进行置乱操作。在双向块扩散过程，置乱后的图像重新被分成若干个大小相同的图像块，最后对图像块进行块扩散操作得到密文图像。仿真结果和安全性分析表明该算法是安全高效的。

Fast image encryption algorithm based on improved Henon map

In order to solve the drawbacks of small chaotic space and poor security when the traditional Henon map was implemented in cryptosystem, this paper designed an improved Henon map. Performance analysis in terms of bifurcation diagram, chaotic orbit, Lyapunov exponent and approximate entropy proved that the improved Henon map had larger chaotic space, better ergodicity and higher chaotic complexity, which made it applicable for developing secure cryptosystem. Based on the improved Henon map, this paper proposed a fast image encryption algorithm. The proposed algorithm consisted of multiple-block substitution and bidirectional block diffusion. In the multiple-block substitution process, it divided the plain image into some blocks with various sizes, and then scrambled these blocks. In the bidirectional block diffusion process, it redivided the scrambled image into several blocks with same size, and carried out the block diffusion operation to obtain the cipher image. Simulation results and security analysis demonstrate that the proposed algorithm is safe and efficient.