中文摘要：

提出了一种基于双光束干涉结构和非线性相关算法的身份认证方法．该方法在传统双光束干涉加密结构中引入基于“随机二值振幅分布”的相位恢复技术，将多幅图像分别编码至对应的稀疏相位分布，并通过叠加复用技术和非线性相关算法，实现了多级别的身份认证功能．其认证过程中不同级别用户所持有的相位密钥是一个稀疏相位分布，数据量更小，便于存储和传输，此外，认证时的输出图像虽然含有标准参考图像的核心信息却具有视觉上的不可分辨性，降低了信息泄露的风险．理论分析和数值仿真结果都证实了该方案的有效性和可行性．

英文摘要：

In this paper, a new approach to identity authentication is proposed, which takes advantage of the two-beam interference setup and the nonlinear correlation technique. According to the traditional two-beam interference encryption/decryption structure, we design a modified iterative phase retrieval algorithm （MIPRA）, which takes the random binary amplitudes as the constraints at the input plane to encode different images （standard reference images） into a set of sparse phase distributions. In the MIPRA, a given random phase distribution serves as a system lock, and it is placed at one of the arms of the two-beam interference setup and keeps unchanged in the whole iterative phase retrieval algorithm but equivalently provides a fixed shifting vector toward the output complex amplitude field. While the peak-to-correlation value （between the output intensity and the original image） reaches a presetting threshold value, or the iterative numer of time reaches a presetting maximum value, the MIPRA stops. Here, the phase lock is assumed to be the same for all the users and thus it is placed and fixed in the system, while the calculated phase distributions vary from the MIPRA to different binary constraints, which are related to different users. Meanwhile, we also study an extension version of the proposed method. By using a superposition multiplexing technique and a nonlinear correlation technique, we can realize a function of hierarchical authentication for various kinds of users through a similar but more smart decision strategy. For example, we adopt the MIPRA four times with different constraints （random binary amplitude distribution） to obtain four phase distributions, the sum of them will be regarded as a final phase key and is designed to the user with the highest privilege. He is then able to pass all the authentication process for each standard reference image with his multiplexed phase key, that is to say, there are obvious peaks in all the nonlinear correlation maps between all the output images