联合空域和小波域的图像加密

针对基于混沌理论的混合域图像加密算法存在加密强度较弱的问题，提出一种新的联合空域和小波域的图像加密算法。首先对原始图像进行一级二维离散小波分解，提取低频小波系数；接着使用二维Sine Logistic映射生成混沌序列，利用该混沌序列使用混沌魔方变换置乱低频子带，然后完成图像逆小波变换。对置乱后的图像，首先使用互绕Logistic映射生成混沌序列用于空域加密密钥，然后联合基于伽罗瓦域上元素乘法和异或的变换技术对像素进行加密；同时，引入混沌扰动和加密反馈技术以实现生成一次性运行密钥。理论分析和实验结果表明，新算法具有密钥空间大、抗重构攻击、抗差分攻击、加密效率可行、安全性强等特点。

Image encryption based on combination of spactial and wavelet domain

Aiming at the problem that hybrid domain image encryption algorithm based on chaos theory has weak encryption strength, a new image encryption algorithm based on the combination of spatial and wavelet domain was proposed. First, one-level two-dimensional discrete wavelet decomposition was performed on the original image to extract the low-frequency wavelet coefficients. Second, using the chaotic sequence generated by 2D Sine Logistic chaotic dynamic system, the low frequency sub-band was scrambled by using chaotic magic transformation, then inverse wavelet transformation was executed on decomposed image.For the scrambled image, a chaotic sequence used for encryption key in spatial domain based on intertwining Logistic map was generated, then the pixels were encrypted by using the combination technology of elemental multiplication in a Galois field with XOR. At the same time, the technology of chaotic disturbance and encryption feedback was introduced to implement one-running key. Theoretical analysis and experimental results show that the proposed algorithm has the advantages of large key space, anti-reconstruction attack, anti-differential attack, feasible encryption efficiency, strong security, and so on.