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arxiv: 2605.16796 · v1 · pith:E5AEMJFCnew · submitted 2026-05-16 · 💻 cs.CR · cs.CV

Watermarks Attack Watermarks: Re-Watermarking as a Generic Removal Strategy

Pith reviewed 2026-05-19 21:17 UTC · model grok-4.3

classification 💻 cs.CR cs.CV
keywords watermarkingadversarial attackswatermark removalimage provenancecopyright protectionre-watermarkingblack-box attack
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The pith

Re-watermarking an already watermarked image reliably suppresses the original signal.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that re-applying a watermark to an image already protected by one suppresses the original watermark's detection. This works across 96 combinations of datasets, victim watermarks, and attack watermarks. The technique needs no gradients, surrogate models, or detection keys. A separate classifier identifies the presence and identity of an existing watermark with accuracies between 0.878 and 0.953. When used together, the steps cut original bit accuracy by 25 to 48 percent and question the strength of current watermarking schemes.

Core claim

Watermark attacks are analogous to watermarking itself because both seek imperceptible changes that trigger a detector. Re-watermarking an already watermarked image therefore reliably suppresses the original signal. Rigorous experiments over 96 dataset-victim-attack combinations confirm the effect without requiring gradients, surrogate models, or keys. A simple classifier detects watermark presence and identity at 0.878-0.953 accuracy. The combined pipeline reduces bit accuracy by at least 25 percent and up to 48 percent.

What carries the argument

The analogy that watermark attacks and watermarking both apply imperceptible perturbations to trigger detectors, allowing one watermark to interfere with another.

If this is right

  • Re-watermarking suppresses the original signal without gradients, surrogate models, or detection keys.
  • A classifier identifies existing watermarks with overall accuracies of 0.878-0.953.
  • Combining identification and re-watermarking reduces bit accuracy by 25 to 48 percent.
  • Current watermarking schemes for provenance and copyright protection face a simple generic attack.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Watermark designers may need to test resistance specifically against other watermarks as a new class of interference.
  • The ability to first identify which watermark is present turns detection into an enabler for targeted removal.
  • The same re-watermarking logic could be tested on audio, video, or text detectors that rely on imperceptible triggers.
  • Multiple successive re-watermarkings might produce compounding suppression effects worth measuring.

Load-bearing premise

Any imperceptible change meant to trigger a detector, including a new watermark, will interfere with an existing watermark's detection independent of the schemes used.

What would settle it

An experiment on a new combination of victim and attack watermarks in which re-watermarking leaves original detection accuracy or bit accuracy essentially unchanged.

Figures

Figures reproduced from arXiv: 2605.16796 by Benjamin I. P. Rubinstein, Maria Bulychev, Neil G. Marchant.

Figure 1
Figure 1. Figure 1: Attack evaluation on MS-COCO (see Fig. 5 of the Appendix for DiffusionDB results). [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Detection metrics before and after apply [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Per-method prediction distribution of the classifier, aggregated over MS-COCO and [PITH_FULL_IMAGE:figures/full_fig_p016_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Per-image normalized quality degradation introduced by each watermarking method, [PITH_FULL_IMAGE:figures/full_fig_p018_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Performance vs. image quality degradation on DiffusionDB. Each watermarked image [PITH_FULL_IMAGE:figures/full_fig_p019_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Visual examples of all attacks from Section 4 applied to a single DiffusionDB image [PITH_FULL_IMAGE:figures/full_fig_p021_6.png] view at source ↗
read the original abstract

Watermarking combines an imperceptible change to an input image that will trigger a detector, to assert provenance and protect intellectual property. The literature has shown great interest in attacks on watermarking schemes: attackers are clearly motivated to steal copyrighted material or circumvent legislated deepfake protections. In this work, we make a simple-yet-powerful observation: that such attacks on watermarking-like watermarks themselves-seek an imperceptible change to an input image (now already watermarked) that will trigger a detector. This analogy comparing watermark attacks to watermarking itself is highly suggestive: that watermarks could be used to attack watermarks. Our first contribution validates this hypothesis. In rigorous experiments spanning 96 combinations of dataset, victim, and attack watermarks, we show that simply re-watermarking an already watermarked image reliably suppresses the original signal, without requiring gradients, surrogate models, or detection keys. Our second contribution is a simple classifier for detecting the presence and identity of an existing watermark in a given image. Surprisingly, experimental findings demonstrate outstanding overall accuracies 0.878-0.953. This result is of independent interest as a security vulnerability: research shows that method-specific attacks achieve substantially stronger removal than black-box attacks. Taken together, watermark identification combined with re-watermarking successfully reduces bit accuracy by at least 25% and up to 48%. Our work constitutes a cheap, generic, and highly effective attack pipeline, calling into question the reliability of current watermarking schemes to such a simple attack, as well as the value of existing sophisticated attacks.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript claims that re-watermarking an already watermarked image reliably suppresses the original watermark signal, serving as a generic removal strategy. This is supported by experiments across 96 dataset-victim-attack combinations showing bit-accuracy drops of 25-48% without gradients, surrogates, or keys. A secondary contribution is a classifier detecting watermark presence and identity with accuracies of 0.878-0.953, which combined with re-watermarking yields the reported suppression.

Significance. If the central claim holds after controls, the work would be significant for digital watermarking and IP protection research. The breadth of 96 empirical combinations provides substantial coverage across schemes and datasets. The watermark-detection classifier is of independent interest as a demonstrated vulnerability. The approach is cheap and black-box, directly challenging the robustness of existing watermarking methods and the necessity of sophisticated attacks.

major comments (2)
  1. [Experimental evaluation] Experimental evaluation: the results across the 96 combinations do not include control baselines using generic imperceptible perturbations (e.g., additive Gaussian noise or JPEG compression) calibrated to the same PSNR/LPIPS as the re-watermarking step. Without this isolation, it remains unclear whether the 25-48% bit-accuracy drop arises from scheme-specific embedding conflict or from generic signal degradation, which is load-bearing for the claim of a distinct 'generic removal strategy'.
  2. [Methods] Methods section: full details on the number of trials per combination, variance or error bars on reported accuracies, and any statistical significance tests for the bit-accuracy drops are absent. This prevents full assessment of the reliability of the 0.878-0.953 classifier accuracies and the removal results.
minor comments (2)
  1. [Abstract] The abstract states 'rigorous experiments' but does not name the specific datasets, which would aid immediate comprehension.
  2. [Introduction] Notation distinguishing victim watermark W_v and attack watermark W_a is introduced but could be defined more formally on first use in the introduction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thoughtful review and constructive suggestions. The comments highlight important aspects for strengthening the experimental validation and methodological transparency of our work on re-watermarking as an attack strategy. We address each major comment below and outline the revisions we will make to the manuscript.

read point-by-point responses
  1. Referee: [Experimental evaluation] Experimental evaluation: the results across the 96 combinations do not include control baselines using generic imperceptible perturbations (e.g., additive Gaussian noise or JPEG compression) calibrated to the same PSNR/LPIPS as the re-watermarking step. Without this isolation, it remains unclear whether the 25-48% bit-accuracy drop arises from scheme-specific embedding conflict or from generic signal degradation, which is load-bearing for the claim of a distinct 'generic removal strategy'.

    Authors: We agree that control experiments with generic perturbations matched for perceptual similarity (PSNR and LPIPS) are necessary to isolate whether the observed bit-accuracy reductions stem from specific watermark embedding conflicts or from non-specific signal degradation. While our re-watermarking method applies a structured perturbation derived from the watermarking process itself—potentially leading to targeted interference rather than random degradation—we acknowledge the value of these baselines for rigorously supporting the claim of a 'generic removal strategy'. In the revised manuscript, we will include additional experiments applying additive Gaussian noise and JPEG compression calibrated to achieve similar PSNR and LPIPS values as the re-watermarking step, and report the corresponding bit-accuracy drops for comparison across the same combinations. revision: yes

  2. Referee: [Methods] Methods section: full details on the number of trials per combination, variance or error bars on reported accuracies, and any statistical significance tests for the bit-accuracy drops are absent. This prevents full assessment of the reliability of the 0.878-0.953 classifier accuracies and the removal results.

    Authors: We concur that including details on the experimental setup, such as the number of trials, measures of variance, and statistical tests, would enhance the reproducibility and credibility of our results. The original experiments were conducted over multiple images per combination to ensure robustness, but these specifics were not fully detailed in the manuscript. We will revise the Methods section to specify the number of trials (e.g., 50-100 images per dataset-victim-attack combination), include error bars or standard deviations in the reported accuracies and bit-accuracy drops, and add statistical significance tests (such as Wilcoxon signed-rank tests or t-tests) to confirm the significance of the observed reductions. revision: yes

Circularity Check

0 steps flagged

No significant circularity; empirical validation is self-contained

full rationale

The paper advances a hypothesis based on an analogy between watermark attacks and watermark embedding, then validates it through direct experimentation on 96 combinations of datasets, victim watermarks, and attack watermarks. Bit-accuracy drops are reported as observed outcomes rather than outputs of any fitted model or self-referential definition. No equations, parameter-fitting steps, or load-bearing self-citations appear in the derivation chain; the central claim rests on external, reproducible trials against multiple independent watermarking schemes. This constitutes a self-contained empirical result against external benchmarks, with no reduction of predictions to inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The paper relies on standard assumptions from digital watermarking and adversarial machine learning; no new free parameters, axioms beyond domain norms, or invented entities are introduced.

axioms (1)
  • domain assumption Watermarking embeds imperceptible signals that can be detected by a corresponding model
    This underpins the analogy between watermark attacks and re-watermarking.

pith-pipeline@v0.9.0 · 5823 in / 1179 out tokens · 56957 ms · 2026-05-19T21:17:01.144463+00:00 · methodology

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    beautiful,

    datasets. [1] show that each of these datasets is characterized by a unique distribution of prompt words, where DiffusionDB emphasizes quality descriptors (e.g., “beautiful,” “highly detailed”), whereas MS-COCO focuses on object descriptions. Following [1], we selected a subset of images as follows:

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    Rank images by aesthetic score [43] and select the top 500 (prioritizing high-quality images for which watermarking is most practically relevant). Baseline Attack ConfigurationsAs a baseline for the performance of our W AW attack, we evaluate each victim watermark against the strongest attacks identified in [1], each applied across a range of strengths: •...

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    (quality levels 1–7). • Rinsing:Regen-2xDiff and Regen-4xDiff iteratively noise and denoise the image via Stable Diffusion v1.4 two and four times, respectively (20, 60, 100, and 10–50 timesteps per pass). D Classifier Analysis and Ablation D.1 Using a Different Diffusion Backbone (SD 3.5) We re-evaluate the classifier on images generated with the more re...

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    unwatermarked

    (lr= 2×10 −5, weight decay=0.01) with a cosine schedule and 10% linear warmup [21]. We maintain an effective batch size of 16 through gradient accumulation and utilize mixed-precision (fp16) training throughout. Final regularization included label smoothing of 0.1 and early stopping with a patience of five epochs. We experiment with two further training s...