A double-image asymmetric cryptosystem is proposed by using cylindrical diffraction and spectrum fusion and compression in the zigzag-scanned domain of discrete cosine transform (DCT). First, each plaintext of double image is converted into spectrum coefficients (SCs) by DCT, and the SCs are zigzag scanned. Second, the first 1/4 of SCs is resized to two low-frequency images, the second 1/4 of SCs is resized to two high-frequency images, while the last 1/2 of SCs is discarded. Third, the two low-frequency and two high-frequency images are fused and merged into three rounds of encryption process by using the complex combination, random phase encoding, and phase reserving-truncation in the cylindrical diffraction transform domain. Finally, the plaintexts of the double image are successfully encrypted into a ciphertext and three private keys with each only 1/8 and totally 1/2 of the size of the plaintext, which gains a high compression efficiency. In the proposed cryptosystem, the quality of the reconstructed image is improved due to the compression in the zigzag-scanned DCT domain, and the security is improved owing to the asymmetric cylindrical diffraction and spectrum-fusion algorithm. The effectiveness and flexibility of the proposed cryptosystem have been validated by the numerical simulation results.

中文翻译：

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使用圆柱衍射和频谱融合与压缩的双图像非对称密码系统

通过在离散余弦变换（DCT）的锯齿形扫描域中使用圆柱衍射，频谱融合和压缩，提出了一种双图像非对称密码系统。首先，通过DCT将双重图像的每个明文转换为频谱系数（SC），然后对SC进行锯齿形扫描。其次，将前1/4个SC调整为两个低频图像，将后1/4个SC调整为两个高频图像，而将最后1/2个SC丢弃。第三，通过在圆柱衍射变换域中使用复杂的组合，随机相位编码和相位保留截断，将两个低频图像和两个高频图像融合并合并为三轮加密过程。最后，将双重图像的明文成功加密为密文和三个私钥，每个私钥的大小仅为明文大小的1/8，总共仅为明文大小的1/2，从而获得了很高的压缩效率。在所提出的密码系统中，由于在之字形扫描的DCT域中进行了压缩，因此改善了重建图像的质量，并且由于非对称圆柱衍射和频谱融合算法而提高了安全性。数值仿真结果验证了所提出密码系统的有效性和灵活性。非对称圆柱衍射和光谱融合算法提高了安全性。数值仿真结果验证了所提出密码系统的有效性和灵活性。非对称圆柱衍射和光谱融合算法提高了安全性。数值仿真结果验证了所提出密码系统的有效性和灵活性。