Abstract: With the application and development of network technology, the security of image data has been aroused the attention of the whole society. A new image encryption algorithm based on wavelet transform and improved gravity model is proposed. The algorithm uses SHA3-256 to generate the initial value of the 3D Logistic chaotic system and the gravity coefficient of improved gravity model. The algorithm is closely related to the original image, which increases the plaintext sensitivity of the algorithm. Then it transforms the image by wavelet transform, uses 3D Logistic chaotic system to scramble the low frequency coefficient and the high frequency coefficient respectively. After the inverse wavelet transform, it uses improved gravity model to substitute pixel value. The experimental results show that the algorithm has a large key space and can effectively resist all kinds of attacks.

Key words: wavelet transform, image encryption, chaotic systems, gravity model

摘要： 随着网络技术的应用和发展，图像数据安全性引起了社会的关注。提出了一种新的基于小波变换和改进的重力模型的图像加密算法。该算法利用SHA3-256生成三维Logistic混沌系统的初始值及改进的重力模型的重力系数，使算法与原始图像密切相关，增加了算法的明文敏感性；对图像进行小波变换，用三维Logistic混沌系统分别对低频系数和高频系数进行置乱，再进行小波逆变换；最后，用改进的重力模型进行像素值扩散。实验结果表明，该算法密钥空间大且可有效抵抗各种攻击。

关键词: 小波变换, 图像加密, 混沌系统, 重力模型