基于混合相位掩码与非线性像素互换的光学图像加密算法

Optical image encryption algorithm based on mixedphase mask and nonlinear pixel swap

为了解决当前光学图像加密技术在信息加密过程中忽略了明文自身特性,且其密文输出为复数函数,增加了密文信息的存储、传输与管理难度的不足,设计了混合相位掩码与非线性像素互换的光学图像加密算法。首先,将明文生成其对应的快速响应QR码,降低斑点噪声的影响;随后,引入SHA-256散列函数,设计非线性像素互换机制,对QR码进行置乱;基于剪切波变换,对置乱后的QR码进行分解,得到4个剪切波系数;利用安全图像与第一个剪切波系数完成互换,将其视为解密私钥;联合安全密钥图像与剩余的3个剪切波系数,基于剪切波逆变换,输出一个过渡图像;利用明文像素来迭代Logistic映射,输出混沌相位掩码,将其与螺旋相位掩码融合,形成一个混合掩码;基于Gyrator变换,对过渡图像进行调制,将其强度分布视为密文。测试数据显示,算法具有更高的加密安全性与抗选择明文攻击能力。

In order to solve the problem as ignoring the characteristics of the plaintext during the process of information encryption, and increasing the difficulty of storing, transmitting and managing ciphertext information induced by its ciphertext output as a complex function in current optical image encryption technology, this paper proposes an optical image encryption algorithm based on mixed phase mask and nonlinear pixel transform.Firstly, the fast response quick response(QR) code was generated to reduce the impact of speckle noise. Then the nonlinear pixel swap mechanism was designed by introducing the SHA-256 hash function to scramble the QR code. Four shearlet coefficients were obtained by decomposing the scrambled QR code based on shearlet transformation. The decryption private key was obtained by interchanging between the security image and the first shearlet coefficient. Combining the security key image and the remaining three Shearlet coefficients, the transition image was output based on inverse Shearlet transform. A mixed mask was formed by fusing the spiral phase mask and chaotic phase mask outputted by using the plaintext pixels to iterate the logistic mapping. Finally, the transition image is modulated based on the Gyrator transform, and its intensity distribution was regarded as a cipher.The test results show that this algorithm has higher encryption security and anti selection plaintext attack ability.