提出了一种基于光学衍射的二值图像加密方法。该方法仅需记录单幅衍射强度图像，加密过程避免了干涉装置，提高了记录效率，且单幅密文的传输更为方便。在加密前，先提取原始二值图像的冗余数据作为密钥保存，再使用光学衍射图像加密方法对原始二值图像加密，得到的衍射强度图像即为密文。解密时使用相位恢复算法进行迭代运算，把先前提取的冗余数据作为输入平面的部分振幅支撑，使算法能够快速收敛，从而完全恢复明文。计算机模拟结果证实了该方法的有效性，也分析了其对剪切和噪音攻击的稳健性。

A method for image encryption by employing the diffraction imaging technique is proposed. Only a single diffraction intensity image is recorded without using interference equipment that makes the method much more efficient, and the transmision of the single ciphertext more convenient. Before encrypting, the redundant data of the original binary image are extracted as the secret key, then the original binary image is encrypted by using optical diffraction image encryption method and the diffraction intensity image is the ciphertext. During image decryption, the redundant datas serve as partial input plane support constraint in phase retrieval algorithm iterative operation, which is employed for making algorithm convergences fastly. Computer simulation results verify the validity of the proposed approach. Its robustness against occlusion and noise attacks are also analyzed.