基于混沌映射的分块循环DNA图像加密算法

数字图像具有数据量大、冗余度高、像素间关联性强等特点，打破数据间关联性及提高敏感性是保护图像信息的关键。针对如何快速有效打破图像像素间强关联性、提高图像数据敏感性等问题，提出基于logistic混沌映射的分块循环DNA图像加密算法。算法采用二次置乱、一次扩散结构，首先通过zigzag变换置乱明文图像，打破明文像素间的强关联性；其次将伪随机序列生成器产生的密钥作为混沌参数进行混沌映射，生成动态DNA编/解码、运算规则，对置乱的明文图像进行DNA编码形成初始密文；然后利用DNA运算规则，对初始密文进行分块循环DNA运算，完成密文扩散，并对DNA碱基进行统计和归一化作为二次混沌密钥；最后采用二次混沌映射生成动态步长规则，对密文进行变步长约瑟夫置乱，利用DNA解码规则形成最终密文图像。实验结果表明，密文图像像素分布均匀、像素间关联性弱、密钥敏感性强、密钥空间足够大，能够有效抵御信息分析、暴力、噪声、剪切等常见攻击，具有较高的安全性。

Block cyclic DNA image encryption algorithm based on chaotic map

Digital image has the characteristics of large amount of data, high redundancy and strong correlation between pixels. Breaking the correlation between data and improving sensitivity is the key to protect image information. Aiming at how to quickly and effectively break the strong correlation between image pixels and improve the sensitivity of image data, this paper proposed a block cyclic DNA image encryption algorithm based on logistic chaotic map. The algorithm adopted the structure of secondary scrambling and primary diffusion. Firstly, it scrambled the plaint image by zigzag transform to break the strong correlation between plaint pixels. Secondly, it used the key generated by random sequence generator as chaotic parameters to generate dynamic DNA coding/decoding and operation rules, and encoded the scrambled plaint image by DNA to form the initial cipher. Then, using the DNA operation rule, it divided the initial cipher into blocks and cyclic DNA operation to complete the cipher diffusion, and counted and normalized the DNA bases into a quadratic chaotic key. It generated the dynamic step size rules by quadratic chaotic map, scrambled the cipher by Joseph variable step length, and formed the final cipher image by using the DNA decoding rules. The experimental results show that the cipher image has uniform pixel distribution, weak correlation between pixels, strong key sensitivity and large key space, which can effectively resist common attacks such as information analysis, violence, noise, clipping and so on.