SwordStamp

SwordStamp adds order-robust detection and semantic-span units to embedding-based semantic watermarks. This artifact contains the exact paper configuration, generation and detection code, the unchanged attack suite, quality evaluation, and deterministic result extraction and plotting.

Paper: Semantic Watermarking with Order-Robust Detection over Sub-sentence Units (arXiv:2608.27666)

Headline results

At 5% false-positive rate and a 90% content-preservation requirement, the scheme-specific embedding displacement attack (EDA-S) achieves:

Relative to their published baselines, SwordStamp and k-SwordStamp reduce EDA-S success by 29.2 and 22.5 percentage points, at clean-fidelity costs of 1.8 and 4.4 points. Their clean detection rates are 94.9% and 97.0%. Under the stronger detector-access EDA-D stress test, maximum quality-gated success is 39.7% on k-SwordStamp versus 65.5% on k-SemStamp.

These results cover English news continuations, one provider model, two provider encoders, and one EDA paraphraser/surrogate pair.

Plot a compiled bundle

visualization consumes only the compiled CSV/Parquet bundle. It fails on missing paper cells rather than drawing a partial figure.

uv sync --frozen --only-group plot --no-install-project
uv run --no-sync python -m visualization extract \
  --bundle results/paper --output results/paper
uv run --no-sync python -m visualization render \
  --bundle results/paper --output results/paper

This writes auditable tables under results/paper/tables/ and seven figures in PNG and PDF under results/paper/figures/. The anonymous review branch includes the compiled bundle; a full run on the release branch creates the same files with python -m visualization compile.

Embedding displacement attack (EDA)

The embedding displacement attack (EDA) is an adaptive whole-text paraphrasing attack. At each output unit it samples K continuations and keeps the candidate with the largest cosine displacement from its source anchor under a surrogate encoder. Because every candidate continues the full rewrite prefix, one objective can reword content, reorder it, and split or merge detector units.

No-box EDA sees the marked text and the public watermark design. It does not query the detector or generator and receives no secret key, provider encoder, or quality oracle.

For bag anchoring, the paper uses attack.bag_agg=min: maximize distance from the nearest source anchor. Reported no-box runs use Qwen/Qwen2.5-3B-Instruct, BAAI/bge-base-en-v1.5, K={1,2,4,8,16,32,64}, temperature 1.0, top-p 0.95, at most 96 tokens per candidate, and at most 512 rewrite tokens.

Other watermark designers can call EDA directly:

from attacks.paraphrasing.adaptive import adaptive_attack_paraphrase

attacked = adaptive_attack_paraphrase(
    texts,
    base_model="Qwen/Qwen2.5-3B-Instruct",
    surrogate_model="BAAI/bge-base-en-v1.5",
    num_candidates=32,
    anchor="positional",       # EDA-P; use "bag" for an order-robust design
    bag_agg="min",
    segmentation_type="sentence",
    segmentation_backend="nltk",
)

For the paper's SwordStamp-aware EDA-S, set anchor="bag", segmentation_type="semspan", semcut_max_words=15, and semcut_window=5. Within this repository the equivalent CLI is:

uv run python -m attacks DATA_PATH --config PRESET \
  --set attack.paraphraser=adaptive \
  --set attack.custom_model=Qwen/Qwen2.5-3B-Instruct \
  --set attack.surrogate_model=BAAI/bge-base-en-v1.5 \
  --set attack.num_candidates=32 \
  --set attack.anchor=bag --set attack.bag_agg=min \
  --set segmentation.attacker_type=semspan \
  --set segmentation.attacker_backend=nltk

DATA_PATH is always the base corpus and PRESET identifies the watermarked cell. See attacks/README.md for all retained attacks and configuration fields.

Exact paper matrix

config/paper.py is the single source of truth. For each of LSH and k-means, scripts/experiments/swordstamp.sh runs this five-rung additive ladder with 64 provider candidates:

1. context-dependent rejection over sentences;
2. best-of-64 selection;
3. a fixed valid set;
4. diversity-aware ranking; and
5. semantic spans with maximum 15 words and comparison window 5.

The grid contains only these ten cells and one no-watermark baseline. PMark is online-only; SAMark uses one flag pattern per run. EDA-D budgets are K={4,8,16,32,64}.

The comparison submodules adapt the public PMark and SAMark evaluation sources only at their dataset/result boundaries and shared false-positive calibration; the watermark algorithms are unchanged.

Complete experiment flow

Prerequisites are Git, uv, Python 3.11, CUDA for model runs, access to the pinned model revisions, and scratch storage.

git clone --recurse-submodules [email protected]:D-Diaa/SwordStamp.git
cd SwordStamp
bash scripts/setup.sh
uv run --frozen python scripts/check_artifact.py

1. Prepare the deterministic, disjoint C4 partitions:

   root@kitploit:~

   uv run --frozen python scripts/prepare_c4.py --output-dir data
   

2. Install and configure the pinned scheduler. The installer prints its user-level side effects before changing anything:

   root@kitploit:~

   bash scripts/install_gpu_scheduler.sh --print-plan
   bash scripts/install_gpu_scheduler.sh --yes
   gpu-scheduler init --gpus 0,1
   gpu-scheduler start
   

3. Preview, then submit every physical shard:

   root@kitploit:~

   for shard in c4-val-def-256 c4-val-def-256b c4-val-def-512; do
     BASE="data/$shard" DRY_RUN=1 bash scripts/experiments/swordstamp.sh
     BASE="data/$shard" DRY_RUN=1 bash scripts/experiments/pmark.sh
     BASE="data/$shard" DRY_RUN=1 bash scripts/experiments/samark.sh
   done
   # Remove DRY_RUN=1 after inspecting the exact DAGs.
   

4. Compile, extract, and render:

   root@kitploit:~

   uv run --frozen python -m visualization all \
     --bundle results/paper --output results/paper
   

The scheduler supplies CUDA_VISIBLE_DEVICES; do not select GPUs by probing nvidia-smi. Full reproduction is a multi-day GPU workload. ARTIFACT.md lists hardware, model revisions, expected outputs, and the claim-to-command map. scripts/experiments/README.md documents resume and force behavior.

Layout and license

• config/, segmentation/, sampling/, watermarking/: SwordStamp.
• attacks/: EDA and the retained attack suite.
• quality/: fidelity and content-preservation evaluation.
• visualization/: paper-only compilation, tables, and Matplotlib figures.
• scripts/experiments/: scheduler-backed exact paper workflows.
• external/: pinned PMark and SAMark comparison submodules.

First-party code is released under the MIT License. Models, datasets, generated text, and comparison submodules retain their own terms; see THIRD_PARTY.md.

Citation

If you use SwordStamp, please cite the paper:

@misc{diaa2026semantic,
  title         = {Semantic Watermarking with Order-Robust Detection over Sub-sentence Units},
  author        = {Abdulrahman Diaa and Jonathan Petit and Florian Kerschbaum},
  year          = {2026},
  eprint        = {2608.27666},
  archivePrefix = {arXiv},
  primaryClass  = {cs.CR},
  url           = {https://arxiv.org/abs/2608.27666},
}

SwordStamp software is authored by Abdulrahman Diaa; the paper authors are Abdulrahman Diaa, Jonathan Petit, and Florian Kerschbaum. Machine-readable software and preferred paper citation metadata is in CITATION.cff.