C2pa Watermark

c2pa-watermark-mcp

C2PA Content Credentials MCP server — embed and verify machine-readable provenance for AI-generated assets, ahead of the EU AI Act Article 50 deadline (2 December 2026).

Why this exists

EU AI Act Article 50 (Regulation (EU) 2024/1689) requires that AI-generated content be machine-readable + detectable as AI-generated. The c2pa.ai_generated assertion is the C2PA spec's mandated way to do that.

The deadline is 2 December 2026 — about 6 months out. Companies that ship user-facing generative tools without C2PA support face fines up to €35M or 7% of global turnover.

This MCP wraps the official c2pa-python SDK (≥0.9.0) as an MCP server so agents can attach C2PA manifests at generation time and verify provenance at runtime. A pure-stdlib HMAC fallback is included for environments where c2pa-python's native deps won't install (Vercel serverless, CI sandboxes, etc.).

Features

• 3 MCP tools — sign_asset, verify_asset, status
• EU AI Act Article 50 ready — auto-injects c2pa.ai_generated assertion
• Pure-stdlib fallback — works without c2pa-python's native deps
• HMAC-SHA256 signatures — tamper-evident manifests
• Optional X.509 chain — via c2pa-python[evm] extra
• Vercel-deployable — see c2pa-watermark-vercel sibling repo

Tools

install

# Core (HMAC fallback, no native deps)
pip install c2pa-watermark-mcp

# With full c2pa-python (X.509 chain)
pip install 'c2pa-watermark-mcp[c2pa]'

# For local development
git clone https://github.com/CSOAI-ORG/c2pa-watermark-mcp
cd c2pa-watermark-mcp
pip install -e .[dev]

usage

Sign an asset (Pro tier)

from c2pa_watermark_mcp import sign_asset, verify_asset, status

# Server health
print(status())
# → {'server': 'c2pa-watermark-mcp', 'c2pa_python_available': False, ...}

# Sign an asset
with open("output.png", "rb") as f:
    asset = f.read()
key = b"my-hmac-key-32-bytes-long-aaaaaa"
result = sign_asset(
    asset_bytes=asset,
    asset_mime="image/png",
    claim_generator="MEOK-SDXL/1.0",
    signing_key=key,
    ai_generated=True,
    assertions=[
        {"label": "c2pa.training", "value": {"model": "sdxl-1.0", "dataset": "internal"}},
    ],
)
print(result["manifest_id"])

# Verify
verdict = verify_asset(asset, result["manifest"], key)
print(verdict)  # {'valid': True, 'reasons': [], ...}

Run as MCP server (stdio)

c2pa-watermark-mcp
# or with full c2pa-python
pip install 'c2pa-watermark-mcp[c2pa]'
c2pa-watermark-mcp

Run via Docker

docker build -t c2pa-watermark-mcp .
docker compose up -d
# status endpoint on http://localhost:8000

Deployment to Vercel

See the companion repo c2pa-watermark-vercel for a serverless wrapper exposing /sign, /verify, /status routes.

Architecture

┌─────────────────────────────────────────────────────────────┐
│                c2pa-watermark-mcp                            │
├─────────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐         │
│  │ sign_asset  │  │verify_asset │  │   status    │         │
│  │  (HMAC +    │  │  (HMAC +    │  │ (health +   │         │
│  │   c2pa.io)  │  │   tamper)   │  │  capability)│         │
│  └─────────────┘  └─────────────┘  └─────────────┘         │
│         │                │                │                  │
│         └────────────────┴────────────────┘                  │
│                          │                                   │
│                   ┌──────┴──────┐                           │
│                   │ HMAC-SHA256 │  (always available)       │
│                   │ + c2pa.io  │   (if c2pa-python installed)│
│                   └──────┬──────┘                           │
│                          │                                   │
│  ┌─────────────┐  ┌──────┴──────┐  ┌─────────────┐         │
│  │  manifest   │  │  signing   │  │  AI-Act     │         │
│  │  generator  │  │   keys     │  │ assertions  │         │
│  └─────────────┘  └─────────────┘  └─────────────┘         │
└─────────────────────────────────────────────────────────────┘

Why we auto-inject c2pa.ai_generated

The C2PA spec defines this as the standard way to disclose AI-generated content. EU AI Act Article 50 says AI content must be "machine-readable and detectable as AI-generated" — the spec's answer is exactly this assertion. Skipping the auto-inject would be a compliance violation waiting to happen.

FAQ

Q: Does this need c2pa-python? A: No. The pure-stdlib HMAC-SHA256 fallback is fully functional for tamper-evident manifests. Install c2pa-python only if you need the full X.509 chain.

Q: Can I sign an asset that's not a PNG/JPEG? A: Yes. The asset_mime parameter is just metadata; the HMAC is over the bytes themselves. Works for video, audio, PDFs, etc.

Q: How do I rotate the signing key? A: Generate a new key, deploy with both OLD_KEY and NEW_KEY, re-sign all manifests with NEW_KEY, then drop OLD_KEY after expiry. This package supports key rotation via the signing_key constructor arg.

Q: Is this production-ready? A: Yes for tamper-evidence (HMAC). For full X.509 C2PA chain + cryptographic non-repudiation, install c2pa-python ≥ 0.9.0.

License

MIT © MEOK AI Labs / CSOAI-ORG