UnMarker: A Universal Attack on Defensive Watermarking

Reports regarding the misuse of $\textit{Generative AI}$ ($\textit{GenAI}$) to create harmful deepfakes are emerging daily. Recently, defensive watermarking, which enables $\textit{GenAI}$ providers to hide fingerprints in their images to later use for deepfake detection, has been on the rise. Yet, its potential has not been fully explored. We present $\textit{UnMarker}$ -- the first practical $\textit{universal}$ attack on defensive watermarking. Unlike existing attacks, $\textit{UnMarker}$ requires no detector feedback, no unrealistic knowledge of the scheme or similar models, and no advanced denoising pipelines that may not be available. Instead, being the product of an in-depth analysis of the watermarking paradigm revealing that robust schemes must construct their watermarks in the spectral amplitudes, $\textit{UnMarker}$ employs two novel adversarial optimizations to disrupt the spectra of watermarked images, erasing the watermarks. Evaluations against the $\textit{SOTA}$ prove its effectiveness, not only defeating traditional schemes while retaining superior quality compared to existing attacks but also breaking $\textit{semantic}$ watermarks that alter the image's structure, reducing the best detection rate to $43\%$ and rendering them useless. To our knowledge, $\textit{UnMarker}$ is the first practical attack on $\textit{semantic}$ watermarks, which have been deemed the future of robust watermarking. $\textit{UnMarker}$ casts doubts on the very penitential of this countermeasure and exposes its paradoxical nature as designing schemes for robustness inevitably compromises other robustness aspects.