基于双向相关扩散与非线性混沌S盒的图像加密算法

Image Encryption Algorithm Based on Bidirectional Correlation Diffusion and Nonlinear Chaotic S-Box

目的当前混沌加密方案主要采用存在迭代周期性的序列与单向扩散机制来实现像素的混淆,设计一种加密算法以解决其抗破译性能较弱的问题。方法设计了基于双向相关扩散与非线性S盒的图像加密算法。借助哈希方案,形成一个与初始图像内容相关的密钥;基于2D混合混沌函数,利用子密钥来设计位置交叉规则,实现明文的像素置乱;基于线性分阶变换,联合混沌随机数组,构建一个16×16的非线性S盒;定义S盒的循环向前移位机制和向前扩散机制,对置乱图像完成正向加密;再更新混合混沌系统的初始条件,构建逆向扩散机制,对正向密文完成反向加密。结果测试数据显示,与已有混沌加密方案相比,在安全性和效率方面,所提方案的优势更大,其时耗时仅为0.59s,且稳定的NPCR和UACI值分别达到了99.74%,33.69%。结论所提加密方案可以抵御网络中外来攻击,可充分保证图像内容的真实性。

The work aims to design an encryption algorithm to solve the problem of poor anti-cracking performance induced by the sequence with iterative periodicity and one-way diffusion mechanism to scramble the pixels in current image encryption algorithm.An image encryption algorithm based on bidirectional correlation diffusion and nonlinear S box was designed.Through hash scheme,a key related to the initial image content was formed.Based on the two-dimensional hybrid chaotic function,the position crossover rule was designed with sub-keys to scramble the pixels of the plaintext.A 16×16 nonlinearity S box was formed based on the linear fractional transformation and the chaotic random array.The forward diffusion mechanism and cyclic forward shift mechanism of S-Box were defined to complete the forward encryption of the scrambled image.Finally,the initial conditions of the hybrid chaotic system were updated to construct the reverse diffusion mechanism for encrypting the forward cipher in reverse direction.The test data showed that compared with the existing chaotic encryption schemes,the proposed scheme had more advantages in security and efficiency,in which the time consumption was only 0.59 s,and the stable NPCR and UACI value was up to 99.74% and 33.69%,respectively.The proposed encryption scheme can resist external attacks in the network and fully protect the authenticity of image content.