基于可Markov分割混沌系统的图像加密算法

为了设计复杂度高、安全性好而计算代价小的图像密码算法，该文从一类新的具有Markov分割性质的混沌系统出发构造了此算法。首先，通过控制此混沌系统的参数并配合时空混沌系统设计了一个密钥流发生器；然后，利用真随机数发生器产生的随机数来扰动系统的初始密钥，以动态生成图像的置换矩阵和加密密钥流；最后，通过利用不同群中的加法混合运算构造扩散函数以增加破译复杂度，以两轮迭代完成了图像加密过程。实验结果表明，此混沌系统产生的密钥流序列有比较好的统计特征，该算法可以破坏原始图像的特征，使得密文图像难以辨识。进一步分析可知，该算法可以很好地抵抗差分分析等其它已知攻击，效率高于一些基于超混沌系统设计的密码算法。此外，此算法计算简单，安全性高，易于实现，具有良好的应用前景。

Image Encryption Algorithm Based on Chaos System having Markov Portion

In order to construct a high complexity, secure and low cost image encryption algorithm, a class of chaos with Markov properties is studied and used to build the encryption algorithm. First, the key stream generator is designed by the Markov Chaos with changeable parameters and the improved spatiotemporal chaos. Then, a true uniform random number generator is used to disturb the original key of the algorithm, which can dynamically change the mixed matrix and the key stream. Finally, the diffusion function is built by two iterations of the round function which is composed of different kinds of additions in different groups to increase the complexity of decipher. The experiments indicate that the key stream possesses good statistical properties, and the characteristic of the original image is broken which makes the cipher image undistinguishable. The further analysis indicates that the proposed algorithm can resist some known attacks like differential attacks, and the proposed algorithm is more efficient than the existed algorithms based on super chaos. Additionally, the proposed algorithm is easy to realize and can satisfy the security and efficiency requirements, which indicates promising applications.