光学加密系统的稳健性直接决定其密文在存储和传输过程中的抗干扰能力,并且通常从密文抗裁剪和抗噪声干扰两方面来衡量。针对联合变换相关器光学并行加密系统的多图并行加密和任意图像再现的功能特点,仿真并分析其稳健性。结果表明,当密文面积受到50%裁剪时,各通道图像解密效果明显降低,部分解密图像与原始图像的相关系数(CC)低至0.2左右。分析其原因并对联合功率谱分布进行优化。仿真结果表明,加密系统不仅稳健性得到显著提升(当密文面积受到60%裁剪时,各通道CC值均大于0.49),且能保持优化前加密系统在抗噪声干扰方面的优势。最后,搭建光学实验系统,验证了该加密系统稳健性提升方法的有效性。

The robustness of an optical encryption system directly determines the anti-jamming capability of the ciphertext in the process of storage and transmission, and is always evaluated in the form of the ability against noise and occlusion attacks. The parallel encryption system for multi-channel images based on a joint transform correlator can encrypt the multi-channel images simultaneously into a single ciphertext, and also recover the arbitrary original images with corresponding keys. The robustness of this system is simulated and analyzed. The results show that the decryption effect of each channel is reduced obviously when the ciphertext area is cut by 50%. The correlation coefficient (CC) values between some original and decryption images get the level of about 0.2. The reason is analyzed and the arrangement of the joint power spectrum is optimized. The simulation results show that not only the robustness of the encryption system is significantly improved, especially when the ciphertext area is cut by 60%, the CC values of all channels are greater than 0.49, but also the advantage on resisting noise attacks can be maintained. Finally, an optical experiment system is built to verify the effectiveness of the proposed method for improving the robustness of the encryption system.