一种混合混沌虚拟光学图像加密方法

Virtual Optical Image Encryption Method Based on Hybrid Chaotic System

用共参数的两种混沌系统生成可置换传统双随机相位编码系统中随机相位模板的新模板.将明文图像编码为相位信息,克服原双随机相位编码系统对第一块相位模板不敏感的缺陷;构建可产生均匀非相关随机序列的广义Fibonacci混沌系统,生成均匀分布的相位模板进行图像加密,提高密钥传输效率及系统对密钥的敏感性;对一次加密得到的复值图像,采用提取其振幅及相位的替代操作进行再加密,解决其像素值不能通过按位“异或”进行替代的问题,使密文图像分布更均匀,信息熵达到7.9958,能有效抵御统计分析攻击.在二次加密中,将产生加密模板的混沌初值与一次加密得到的密文联系,像素数改变率达到0.995239,更接近理想期望值,增强了系统对明文的敏感性,有效抵御选择明文攻击.仿真实验表明,该方法有效增加了密钥空间和密钥敏感性,提高了加密系统加密效率和安全性.

In this paper,two chaotic systems with common parameters were used to generate new templates that could replace the random phase templates of the traditional double random phase encoding system.The plaintext image was encoded as phase information to overcame the insensitivity of the first random phase template of the original traditional double random phase encoding system.A generalized Fibonacci chaotic system,which could generate uniform and unrelated random sequences,was constructed to generate evenly distributed phase templates for image encryption and improve the efficiency of key transmission and the sensitivity of the keys.The complex-valued image obtained by the first encryption was replaced by extracting its original amplitude and phase for re-encryption.Therefore the problem that the pixel values of the complex-valued image could not be substituted by bitwise-operation of "xor"was solved,and the pixel value distribution of the ciphertext image became more uniform.The entropy of information reached 7.995 8,which could effectively resist statistical analysis attacks.In the second encryption,the chaotic initial value of the encryption template was connected with the first encryption ciphertext.The number of pixels change rate of 0.995 239 was closer to the ideal expected value.The connection enhanced the sensitivity of the plaintext and the ability of the resistance to choice plaintext attack.Simulation results show that this method can effectively increase the key space and the sensitivity of the keys.Moreover the encryption efficiency and the security of the encryption system are improved effectively.