为了提高密文的安全性, 设计了基于混合相位掩码与Gyrator小波变换的光学图像加密算法。基于Logistic映射, 利用明文像素对其迭代, 生成一个随机相位掩码, 引入Fresnel波带与Hilbert相位函数, 获取二者对应的相位掩码, 通过对这三个相位掩码进行组合, 形成一个混合相位掩码, 对输入明文进行调制处理; 联合Gyrator变换与小波变换, 构建Gyrator小波变换机制, 根据明文像素迭代Logistic映射所输出的混沌序列来计算其旋转角度, 获取明文Gyrator频谱对应的4个子带; 对这些子带进行位置复用, 借助幅度-相位截断技术, 获取相应的密文与相位信息, 而相位信息则视为解密密钥, 以准确复原明文。实验数据表明: 与当前非对称光学加密机制相比, 所提算法具有更高的密文安全性与抗明文攻击能力。

In order to improve the security of cipher, an optical image encryption algorithm based on mixed phase mask and Gyrator wavelet transform was designed. A random phase mask was generated by using a plaintext pixel to iterate the Logistic map, and two phase masks were obtained by introducing the Fresnel zone plate and the Hilbert phase function, which formed a mixed phase mask y combining the three phase masks to modulate the input plain image. The Gyrator wavelet transform mechanism was constructed by combining Gyrator transform and wavelet transform, and four subbands corresponding to the Gyrator spectrum of the plain was obtained by using the chaotic sequence produced by the iterative Logistic mapping with the plaint pixel to calculate its rotation angle. By using amplitude-phase truncation technique, the corresponding cipher and phase information can be obtained by position multiplexing of these subbands, and the phase information was regarded as the decryption key for obtaining the plain. The experimental data shows that the proposed algorithm had higher cryptographic security and anti-plain attack ability compared with the current asymmetric optical encryption mechanisms.