In 2017, an efficient chaotic image cipher with dynamic lookup table driven by bit-level permutation strategy (ICDLT) was proposed (Hu et al. Nonlinear Dyn 87:1359–1375). The chaotic cipher adopts a plaintext-related image encryption mechanism as an efficient measure against chosen-plaintext/ciphertext attack. ICDLT is composed of four basic parts: inter-pixel permutation, sequential addition, intra-pixel permutation and diffusion processes, where two kinds of permutation are both related to the plaintext. Although ICDLT is built on complex nonlinear dynamics, we found that it is still vulnerable against chosen-plaintext attack and its individual sub-keys can be recovered using a divide-and-conquer strategy. Benefiting from the essential structure of ICDLT and the intrinsic properties of Latin square, the proposed attack requires only \( (8 \cdot N^2 +256 + n_c \cdot (2 \cdot N -1))\) plain images, where \(N^2\) is the size of the image and \(n_c\) is the number of cipher images that need to be cracked. Furthermore, we summarize a more general framework which is beneficial for cryptanalyzing a class of plaintext-related image ciphers. Finally, we propose an improved scheme based on the designed plaintext-related XOR encryption (PR-XOR) module to enhance the security of ICDLT. Theoretical analysis and experiments prove that the improved scheme not only maintains the excellent statistical performances of the original one, but also can resist various attacks.

在2017年，提出了一种有效的带有动态查找表的混沌图像密码，该密码表由位级排列策略（ICDLT）驱动（Hu等人，Nonlinear Dyn 87：1359-1375）。混沌密码采用与明文相关的图像加密机制，作为针对选择明文/密文攻击的有效措施。ICDLT由四个基本部分组成：像素间置换，顺序加法，像素内置换和扩散过程，其中两种置换都与明文有关。尽管ICDLT建立在复杂的非线性动力学之上，但我们发现它仍然很容易受到明文攻击，并且可以使用分而治之的策略来恢复其单个子密钥。得益于ICDLT的基本结构和拉丁方的内在属性，拟议的攻击仅需\（（8 \ cdot N ^ 2 +256 + n_c \ cdot（2 \ cdot N -1））\）普通图像，其中\（N ^ 2 \）是图像的大小而\（n_c \）是需要破解的密码图像的数量。此外，我们总结了一个更通用的框架，该框架有助于对一类与明文相关的图像密码进行密码分析。最后，我们提出了一种基于设计的与明文相关的XOR加密（PR-XOR）模块的改进方案，以增强ICDLT的安全性。理论分析和实验证明，改进后的方案不仅保持了原有方案的优良统计性能，而且可以抵抗各种攻击。