Modern image processing tools have made it easy for attackers to crop the region or object of interest in images and paste it into other images. The challenge this cropping-paste attack poses to the watermarking technology is that it breaks the synchronization of the image watermark, introducing multiple superimposed desynchronization distortions, such as rotation, scaling, and translation. However, current watermarking methods can only resist a single type of desynchronization and cannot be applied to protect the object's copyright under the cropping-paste attack. With the finding that the key to resisting the cropping-paste attack lies in robust features of the object to protect, this paper proposes a self-synchronizing object-aligned watermarking method, called SSyncOA. Specifically, we first constrain the watermarked region to be aligned with the protected object, and then synchronize the watermark's translation, rotation, and scaling distortions by normalizing the object invariant features, i.e., its centroid, principal orientation, and minimum bounding square, respectively. To make the watermark embedded in the protected object, we introduce the object-aligned watermarking model, which incorporates the real cropping-paste attack into the encoder-noise layer-decoder pipeline and is optimized end-to-end. Besides, we illustrate the effect of different desynchronization distortions on the watermark training, which confirms the necessity of the self-synchronization process. Extensive experiments demonstrate the superiority of our method over other SOTAs.

翻译：现代图像处理工具使攻击者能够轻易裁剪图像中的感兴趣区域或对象，并将其粘贴到其他图像中。这种裁剪粘贴攻击对水印技术带来的挑战在于，它会破坏图像水印的同步性，引入多重叠加的失同步失真，例如旋转、缩放和平移。然而，当前的水印方法仅能抵抗单一类型的失同步，无法应用于保护裁剪粘贴攻击下对象的版权。基于对抗裁剪粘贴攻击的关键在于保护对象的鲁棒特征这一发现，本文提出了一种名为SSyncOA的自同步对象对齐水印方法。具体而言，我们首先约束水印区域与保护对象对齐，然后通过归一化对象的恒定特征（即其质心、主方向和最小包围正方形）分别同步水印的平移、旋转和缩放失真。为使水印嵌入保护对象中，我们引入了对象对齐水印模型，该模型将真实裁剪粘贴攻击整合到编码器-噪声层-解码器流程中，并进行端到端优化。此外，我们阐述了不同失同步失真对水印训练的影响，这证实了自同步过程的必要性。大量实验证明了我们的方法相对于其他最先进方法的优越性。