Extend the development-only benchmark family from images to audio and video, and close four research directions from the watermark-landscape map with local, revision-pinned evidence. Benchmark schema: media_type audio and video rows, audioseal and videoseal adapters with media-checked adapter binding, sample-domain audio fidelity (SNR with unbounded_identical), frame-domain video fidelity (mean PSNR, changed-frame fraction), and per-frame temporal evidence in videoseal detection records. The report accepts all three media types and carries SNR columns. Audio: shared pinned AudioSeal oracle, synthetic and system-voice speech cohorts with matched negatives, codec, noise, removed, and forged arms, and the provenance experiment proving visual-only video cleaning leaves the audio bitstream and watermark verdict invariant. Video: TorchScript-only VideoSeal oracle (the pip package is unusable on macOS arm64 and its loader resolves paths relative to cwd), video cohort with crf/scale/fps attacks and four-state arms, temporal evaluation measuring the crf decay curve, the frame-aggregation matrix (computed locally after finding the TorchScript build ignores the aggregation argument), and real provider clips as carriers. Forgery: double-embedding study showing the last writer wins completely under both oracles, scoped remover-trace probe, and the forged/ removed cohort arms encoding each scheme's correct expected verdict (presence rule for audioseal, message rule for videoseal). C2PA resolution: measured the five vendors' resolver contracts and the C2PA 2.2 18.10.5 privacy gradient; product decision recorded that this tool never resolves over the network. A registry guard pins the published resolution-API set. Gate: ruff and pyright src/ clean, 2114 passed / 3 skipped; maintain.sh stops only on the known unfixed lightning 2.6.5 CVEs, pre-existing.
3.9 KiB
Watermark forgery study
Development-only study, run on 2026-09-07 from
scripts/watermark_forgery_study.py, opening the forgery/remover-forensics
direction from the original research map. It measures the four-state model
(clean / marked / removed / forged) and the double-embedding question for both
pinned oracles: does embedding message B over an A-marked artifact leave A,
B, or mutual interference?
Carriers: the tone-stack audio carrier, the synthetic moving-gradient video
clip, and the real committed Sora clip. Message B is the oracle's message
generator at seed 8. Everything local; artifacts under .local-eval/.
The double-embedding answer: the last writer wins, completely
| Cell | AudioSeal acc vs A | vs B | VideoSeal (gradient) vs A | vs B | VideoSeal (real Sora) vs A | vs B |
|---|---|---|---|---|---|---|
| marked A | 1.000 | 0.44 | 1.000 | 0.47 | 1.000 | 0.47 |
| removed | 0.50 (presence 0.28) | 0.44 | 0.57 | 0.48 | 1.000 | 0.47 |
| forged B on clean | 0.44 | 1.000 | 0.47 | 1.000 | 0.47 | 1.000 |
| forged B on marked A | 0.44 | 1.000 | 0.47 | 1.000 | 0.48 | 0.99 |
| forged B on removed | 0.56 | 0.875 | 0.47 | 1.000 | 0.47 | 1.00 |
Embedding B over marked A reads as pure B: the original message decays to coin-flip accuracy under both schemes, on synthetic and real content alike. There is no mutual interference and no residue of A. With an unkeyed, openly published embedder this is the expected outcome - and now it is a measurement, not an assumption. The forensic consequence: payload attribution without key control is meaningless against an attacker who can run the same open embedder; only presence detection survives, and even that carries the attacker's payload. Provider schemes that rely on secret keys are a different question this study cannot answer.
Two boundary observations travel with the table:
- The removal transform is carrier-dependent, as the cohorts already showed: 10 dB noise removes the tone stack (presence 0.28) and crf 23 removes the gradient clip (0.57), but the real Sora clip keeps a perfect 1.000 decode through the same crf 23 - the same number the temporal study recorded.
- A forged row reads
detectedunder the AudioSeal presence rule (the label carries the foreign payload) andnot_detectedunder the VideoSeal message-accuracy rule. Both cohort fixtures encode their scheme's correct expected value, and the benchmark docs state the two rules side by side.
Remover-trace probe (scoped first evidence)
High-to-low frequency band energy ratio on clean versus noise-removed audio: the tone stack jumps from 8.6e-05 to 2.3e-02 (a 269x trace), the pinkish carrier 0.016 to 0.039, and the white-noise carrier does not separate at all (0.330 to 0.332) - a noise carrier absorbs a noise remover. This detects the trace of THIS study's gaussian-noise removal only; it is not a general remover detector, and the probe JSON says so in its scope field.
Cohort arms
The audio cohort (v2, 20 cases) and video cohort (v2, 15 cases) now carry the
four states as strict manifest rows: removed rows where the transform
measurably destroys the mark (audio: noise on tone stack; video: crf 23 on
both synthetic carriers), and forged rows embedding message B with the
scheme-correct expected verdict. Zero expected-result mismatches in both
recorded runs.
Pins
Study script
sha256:3985522c862ac44a0c7ef8aa02946a11701439a94d67f5867f00819f638c032b,
case rows
sha256:03d446c08a5daed623a4be2980e097bb8bbc0cd7a6d3ab3f931d25aa58570a16.
Oracles and checkpoints are pinned as in the kernel document.
Follow-ups
- A keyed-scheme perspective needs a scheme with actual key control; WmForger and WMCopier diffusion-attack baselines remain the map's heavyweight item.
- A general remover-trace detector would need features beyond one band ratio and validation against removals this project did not produce.