基于干涉原理和相位恢复算法的图像加密系统

以基于相位恢复算法和光学干涉原理为基本理论依据,提出了一种新的全相位光学图像加密系统。该加密系统利用一块随机相位板作为加密密钥,在其作用下输入图像被数值加密成两块相位板。这两块相位板的衍射图样视觉上无法分辨其内容,但却包含了解密所需要的信息。加密过程中,加密密钥与待加密图像分别作为输入平面和输出平面上的约束条件,在干涉原理的基础上通过迭代运算得到加密结果,即输入面上不同于加密密钥的另一个相位板的相位分布以及傅立叶频域上的相位分布。加密密钥的引入起到了置乱系统输入面相位分布的作用。解密过程中,加密过程中使用的随机相位板和迭代过程中生成的两块相位板缺一不可。计算机仿真实验结果表明,本文提出的加密系统具有算法收敛快、加密结果不存在非线性双随机相位加密和干涉加密方法中发现的信息泄露问题的优点。

Image encryption system based on interference principle and phase retrieval algorithm

A novel fully phase encryption system is proposed based on optical int erference principle and iterative phase retrieval algorithm.In the proposed encryption system,a random phase mask is applied as the unique encryption key.With the help of encryption key,the input secret image is numerically encoded into two phase mas ks,from which the diffraction patterns are visibly unrecognizable but comprise sufficient information for decryption.The image to b e encrypted and the encryption key are respectively used as the constraints in the input and output planes,from wh ich the phase distributions of the encrypted results,i.e., two phase masks respectively placed in the input plane and the Fourier doma in,can be calculated by using the proposed iterative phase retrieval algorithm.The encryption key used in the iterative process intr oduces the pixel scrambling of phase distribution in the input plane.Both the random phase mask and the two pha se masks produced by using the iterative algorithm are indispensable in decryption.Computer simulations demonstrate that the algor ithm achieves a very fast convergence and high security-level.It also can be shown that there is no informat ion disclosure problem in nonlinear double-random-phase encryption or interference-based encryption systems.