混沌相幅变换耦合像素替代的图像加密算法研究
Image encryption algorithm based on chaos phase-amplitude transformation operator coupling pixel substitution

为有效保护图像在开放的网络环境中安全传输，防止信息被窃取，设计了混沌相幅变换算子耦合像素替代的图像加密算法. 首先将256 bit的外部密钥分割为8个子块，以此设计迭代函数初始参数的估算模型，从而生成两个密钥；引入离散傅里叶变换，将图像转变成相与幅度成分；基于第一个密钥，通过迭代Tent映射，生成伪随机图像的相与幅度，并构造线性叠加模型，将明文与随机图像的相与幅度叠加，借助逆离散傅里叶变换，得到置乱图像；再根据第二密钥，基于Logistic映射，设计像素替代模型，改变置乱图像的像素值，在时域与频域内同步完成加密. 仿真实验结果显示该算法具有较高的安全性，能够有效抵御明文攻击，与当前单域图像加密算法相比，具有更高的加密效率.
In order to effectively prevent the image information from being stolen during the image was transmitting in the open network environment，the image encryption algorithm based on chaos phase-magnitude transformation operator coupling pixel substitution was proposed in this paper. Firstly，the permutation image was obtained by introducing the discrete Fourier transformation to covert the image into phase and amplitude components，as well as iterating the Tent map to generate phase and amplitude transformation operators. Then the pixel substitution was designed by Logistic map to change the pixel value of permutation image to synchronization encryption image in time domain and frequency domain. Simulation results showed that this algorithm had high security to effectively resist the plaintext attack and comparison with current image encryption，this algorithm had higher encryption efficiency