Image encryption plays an essential role in the community of image security. Most existing image encryption approaches adopt a permutation–diffusion scheme to permute pixel positions and change pixel values separately. One limitation of this scheme is that it has a high risk of being cracked. To solve this problem, we propose an approach that jointly permutates and diffuses (JPD) the pixels in a color image for encryption. First, a 4D hyperchaotic system with two positive Lyapunov exponents is used to generate a sequence for almost all encryption procedures. To enhance security, the plain image’s information is introduced to the hyperchaotic system’s initial parameters. Then, the hyperchaotic sequence is used to permute and diffuse the pixels in images jointly. More specifically, two index matrices that determine which pixels will be permuted and diffused and one mask matrix that determines how the pixels will be diffused are generated by the hyperchaotic sequence. We test the proposed JPD with several popular images. Experimental results and security analysis demonstrate that the JPD is capable of resisting various types of attacks. Moreover, the JPD can accelerate the encryption process. All these indicate that the JPD is effective and efficient for color image encryption.

中文翻译：

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基于联合置换和扩散的彩色图像加密

图像加密在图像安全社区中起着至关重要的作用。大多数现有的图像加密方法都采用置换扩散方案来置换像素位置并分别更改像素值。该方案的一个局限性在于它极有可能被破解。为了解决此问题，我们提出了一种对彩色图像中的像素进行联合置换和扩散（JPD）以进行加密的方法。首先，具有两个正Lyapunov指数的4D超混沌系统用于生成几乎所有加密过程的序列。为了增强安全性，将普通图像的信息引入到超混沌系统的初始参数中。然后，使用超混沌序列来联合置换和扩散图像中的像素。进一步来说，超混沌序列生成两个索引矩阵，用于确定将对像素进行置换和扩散，以及一个掩码矩阵，用于确定将如何扩散像素。我们用几个流行的图像测试了建议的JPD。实验结果和安全性分析表明，JPD能够抵抗各种类型的攻击。而且，JPD可以加快加密过程。所有这些表明，JPD对于彩色图像加密是有效的。