提出了一种基于双随机相位编码技术的非线性双图像加密方法，并分析了其安全性。在该方法中，加密过程和解密过程以及加密密钥和解密密钥均不相同。加密过程具有非线性，解密过程则是线性的。将两幅待加密图像复合为复振幅图像，并利用双随机相位编码技术和切相傅里叶变换进行加密，加密过程中生成两个解密密钥，解密过程则在经典的基于4f系统的双随机相位编码系统中完成。相比经典的双随机相位加密技术和基于切相傅里叶变换的单图像加密技术，该加密方法的安全性更高，它能够抵御最近提出的基于两步振幅相位恢复算法的特定攻击。理论分析和仿真实验结果都证明了此加密方法的可行性和安全性。

A new method of image encryption and decryption is proposed, where the encryption process is different from the decryption and the encryption keys are also different from the decryption keys. The encryption is nonlinear for the sake of security enhancement while the decryption is linear. Two original images are combined as a complex amplitude image and encrypted based on classical double random phase encoding (DRPE) and phase-truncated Fourier transform (PTFT). Two private keys are generated in the encryption process and the decryption can be performed by the double random phase encoding scheme. Compared with the classical DRPE and PTFT-based single-image encryption, the proposed method is more secure and has resistance against on the specific attack that is based on two-step amplitude-phase retrieval algorithm. Numerical simulations are carried out to demonstrate the validity and security of the proposed scheme.