NOWA：用于不可见拍摄指纹与篡改定位的零空间光学水印
NOWA: Null-space Optical Watermark for Invisible Capture Fingerprinting and Tamper Localization
把相机光圈的相位掩码当作物理密钥，使水印落在成像算子的零空间里，从而在拍摄端嵌入不可见、不可伪造的取证签名；对做图像取证、防伪与安全成像的研究者，这提供了一条从光学前端到重建网络联合设计的思路，且篡改定位只需将图像投影回相机零空间检测像素级不一致。
原文依据 a phase mask in the camera aperture produces a Null-space Optical Watermark (NOWA) that lies in the Null Space of the imaging operator
摘要译文
由模型翻译 · 术语统一 · 请对照原文核对关键结论随着现代编辑工具能够生成高度逼真的伪造内容，确保数字图像的真实性与所有权日益困难。现有的图像保护系统主要依赖数字水印，而数字水印容易受到复杂的数字攻击。为克服这一局限，我们提出一种光学-数字混合框架，在图像形成过程中引入物理认证线索，并通过学习式重建过程将其保留下来。在光学层面，相机光圈中的相位掩码产生一种零空间光学水印（NOWA），该水印位于成像算子的零空间中，因而在拍摄所得图像中保持不可见。随后，零空间网络（NSN）执行测量一致的重建，在保留 NOWA 签名的同时输出高质量的保护图像。该设计通过将图像投影到相机的零空间并检测像素级不一致来实现篡改定位。我们的设计保持了感知质量，能够抵抗压缩等常见退化，并建立起一种结构性的安全不对称性：在无法获取光学参数或 NSN 参数的情况下，攻击者无法伪造 NOWA 签名。仿真实验与原型相机实验表明，与最优的数字水印方法和基于学习的认证方法相比，本方法在图像质量保持与篡改定位精度方面具有有竞争力的性能。
英文原文摘要 1478 字符
Ensuring the authenticity and ownership of digital images is increasingly challenging as modern editing tools enable highly realistic forgeries. Existing image protection systems mainly rely on digital watermarking, which is susceptible to sophisticated digital attacks. To address this limitation, we propose a hybrid optical-digital framework that incorporates physical authentication cues during image formation and preserves them through a learned reconstruction process. At the optical level, a phase mask in the camera aperture produces a Null-space Optical Watermark (NOWA) that lies in the Null Space of the imaging operator and therefore remains invisible in the captured image. Then, a Null-Space Network (NSN) performs measurement-consistent reconstruction that delivers high-quality protected images while preserving the NOWA signature. The proposed design enables tamper localization by projecting the image onto the camera's null space and detecting pixel-level inconsistencies. Our design preserves perceptual quality, resists common degradations such as compression, and establishes a structural security asymmetry: without access to the optical or NSN parameters, adversaries cannot forge the NOWA signature. Experiments with simulations and a prototype camera demonstrate competitive performance in terms of image quality preservation and tamper localization accuracy compared to state-of-the-art digital watermarking and learning-based authentication methods.