authentica 🔍

AI content authenticity detection for Python.
Detect C2PA content credentials, invisible watermarks, and image forensics anomalies — all in one pip install.

Inspired by ExifTool's philosophy: never trust the extension, always read the bytes.

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What it does

Capability	What is detected	How
C2PA / Content Credentials	Manifest presence, COSE signature validity, all assertions (creator, AI gen, training rights, actions)	JUMBF box parsing + CBOR decoding of JPEG APP11 / PNG iTXt chunks
Passive watermark detection	Invisible frequency-domain watermarks (DWT, DCT, FFT-peak analysis)	Blind detection — no original image needed
Image forensics	ELA inconsistency, camera noise anomalies, GAN/diffusion grid artifacts	Error Level Analysis + noise residual + FFT cross-peak detection
Heatmap output	Visual per-pixel influence maps	numpy + matplotlib

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Install

pip install authentica

For full heatmap support:

pip install "authentica[docs]"

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Quick start

Python API

from authentica import scan

result = scan("photo.jpg")
print(result.summary())
# [photo.jpg]  type=image/jpeg  trust=72/100  c2pa=✓  watermark=✗

# C2PA manifest
if result.has_c2pa:
    for assertion in result.c2pa.assertions:
        print(assertion.label, "—", assertion.description)

# Watermark heatmap
if result.has_watermark:
    result.watermark.save_heatmap("watermark_heatmap.png")

# Forensics heatmap
result.forensics.save_ela_heatmap("ela.png")

# Full JSON output
import json
print(json.dumps(result.to_dict(), indent=2))

Individual analyzers

from authentica.c2pa import C2PAReader
from authentica.watermark import WatermarkDetector
from authentica.forensics import ForensicsAnalyzer

# C2PA only
c2pa = C2PAReader().read("photo.jpg")
print(c2pa.claim_generator)   # e.g. "Adobe Photoshop 25.0"
print(c2pa.signature_valid)   # True / False

# Watermark only
wm = WatermarkDetector().detect("photo.jpg")
print(f"Watermark: {wm.detected}  confidence: {wm.confidence:.0%}")
wm.save_heatmap("wm.png")

# Forensics only
forensics = ForensicsAnalyzer().analyze("photo.jpg")
print(f"Anomaly score: {forensics.anomaly_score:.0%}")
forensics.save_ela_heatmap("ela.png")
forensics.save_noise_heatmap("noise.png")

CLI

# Full scan
authentica scan photo.jpg

# Full scan with JSON output
authentica scan photo.jpg --json

# Scan and save watermark heatmap
authentica scan photo.jpg --heatmap wm.png

# C2PA only
authentica c2pa photo.jpg

# Watermark only, save heatmap
authentica watermark photo.jpg --save-heatmap wm.png

# Forensics only, save both heatmaps
authentica forensics photo.jpg --save-ela ela.png --save-noise noise.png

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Architecture

authentica/
├── core.py                   # scan() — unifies all analyzers
├── c2pa/
│   └── reader.py             # JUMBF/CBOR C2PA manifest parser
├── watermark/
│   └── detector.py           # DCT + DWT + FFT watermark detection
├── forensics/
│   └── analyzer.py           # ELA + noise residual + frequency forensics
├── utils/
│   └── file_type.py          # Magic-byte file type detection
└── cli/
    └── main.py               # Rich CLI (Click + Rich)

Data Flow

flowchart TD
    A["User calls scan(path, options)"] --> B["Detect file type using magic bytes"]
    B --> C{"File is image?"}
    C -->|Yes| D["Run Watermark Detector"]
    C -->|No| E["Skip Watermark"]
    D --> F["Run Forensics Analyzer"]
    E --> F
    B --> G{"Run C2PA enabled?"}
    G -->|Yes| H["Run C2PA Reader"]
    G -->|No| I["Skip C2PA"]
    H --> J["Aggregate Results"]
    I --> J
    F --> J
    J --> K["Compute Trust Score"]
    K --> L["Return ScanResult"]

    %% Subprocesses
    subgraph "Watermark Detection"
        D1["DCT anomaly scan"]
        D2["DWT energy analysis"]
        D3["FFT spectrum peaks"]
        D --> D1
        D1 --> D2
        D2 --> D3
    end

    subgraph "Forensics Analysis"
        F1["Error Level Analysis"]
        F2["Noise residual analysis"]
        F3["Frequency domain anomaly"]
        F --> F1
        F1 --> F2
        F2 --> F3
    end

    subgraph "C2PA Processing"
        H1["Extract JUMBF boxes"]
        H2["Parse CBOR payloads"]
        H3["Decode claims/assertions"]
        H4["Map to ExifTool tags"]
        H --> H1
        H1 --> H2
        H2 --> H3
        H3 --> H4
    end

    subgraph "Result Aggregation"
        J1["Collect analyzer outputs"]
        J2["Handle errors gracefully"]
        J3["Create ScanResult object"]
        J --> J1
        J1 --> J2
        J2 --> J3
    end

The main flow follows this pattern:

1. File type detection using magic bytes (never trusts extensions)
2. Conditional analyzer execution based on file type and user options
3. Result aggregation into a unified ScanResult with trust scoring
4. Error handling that gracefully degrades when individual analyzers fail

How it compares to ExifTool

ExifTool (Perl)	Authentica (Python)
Reads metadata from any file via magic bytes	Same — detects file type from bytes, never extension
Walks binary container formats (EXIF, XMP, IPTC)	Walks JUMBF boxes, decodes CBOR C2PA structures
Outputs structured key-value metadata	Outputs structured Python dataclasses + JSON
CLI: exiftool photo.jpg	CLI: authentica scan photo.jpg
50k lines of Perl	Pure Python, typed, tested

C2PA manifest parsing — how it works

C2PA stores a manifest store as a JUMBF (ISO 19566-5) container:

JPEG file
  └── APP11 markers (0xFFEB) — concatenated in sequence order
       └── JUMBF superbox  (TBox='jumb')
            └── JUMBF description box (TBox='jumd', UUID=c2pa UUID)
                 └── CBOR payload — the manifest store
                      ├── active_manifest reference
                      └── manifests map
                           └── claim (CBOR)
                                ├── claim_generator
                                ├── assertions[] — JUMBF URI references
                                └── COSE_Sign1 signature

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Supported formats

Format	C2PA	Watermark	Forensics
JPEG	✓	✓	✓
PNG	✓	✓	✓
WebP	—	✓	✓
TIFF	—	✓	✓
PDF	✓ (basic)	—	—
MP4/MOV	planned	—	—

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Development

# Clone and install in dev mode
git clone https://github.com/yourusername/authentica
cd authentica
pip install -e ".[dev]"

# Run tests
pytest

# Lint + format
ruff check src/
ruff format src/

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Contributing

Contributions welcome! See CONTRIBUTING.md.

Ideas for future modules:

• authentica.llm — LLM-generated text detection (perplexity, KGW watermark)
• authentica.video — frame-level C2PA + watermark analysis
• authentica.synthid — Google SynthID watermark detection

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License

MIT — see LICENSE.

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Acknowledgements

• C2PA Specification — Coalition for Content Provenance and Authenticity
• ExifTool — Phil Harvey's metadata reader (inspiration for the magic-byte approach)
• invisible-watermark — DCT/DWT watermark methods
• Content Authenticity Initiative

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v0.2.0 — ExifTool feature parity update

Inspired by studying the ExifTool source (Perl), this release adds full metadata reading and cross-platform support.

New commands

# Read all metadata (like: exiftool FILE)
authentica meta photo.jpg
authentica meta photo.jpg --json          # machine-readable JSON
authentica meta photo.jpg --csv           # CSV row
authentica meta photo.jpg --gps-dms      # GPS as deg°min'sec"

# Compare metadata between two files (like: exiftool -diff FILE1 FILE2)
authentica diff original.jpg edited.jpg
authentica diff original.jpg edited.jpg --json

# Batch scan a directory (like: exiftool -r -json DIR)
authentica scan-dir /photos --json
authentica scan-dir /photos --csv --out metadata.csv
authentica scan-dir /photos --ext jpg --ext png --progress

# Extract embedded thumbnail (like: exiftool -ThumbnailImage -b FILE)
authentica thumbnail photo.jpg --out thumb.jpg

# Platform info (like: exiftool -ver -v)
authentica version --verbose

New Python API

from authentica import MetadataReader, diff_metadata, BatchScanner

# Full metadata read — EXIF, IPTC, XMP, GPS, ICC, ID3, QuickTime
meta = MetadataReader().read("photo.jpg")
print(meta.exif["Make"], meta.exif["Model"])
print(meta.gps.coord_format("dms"))         # 41° 53' 32.00" N, 12° 29' 24.00" E
print(meta.composite["Aperture"])           # f/2.8
print(meta.composite["ShutterSpeed"])       # 1/500
print(meta.md5, meta.sha256)               # file integrity hashes

# Metadata diff
diff = diff_metadata("original.jpg", "edited.jpg")
print(diff.summary())
for entry in diff.changed:
    print(f"{entry.tag}: {entry.value_a!r} → {entry.value_b!r}")

# Batch scan
scanner = BatchScanner(extensions={".jpg", ".png"}, recurse=True, progress=True)
for path in scanner.walk("/photos"):
    meta = MetadataReader().read(path)
    print(path.name, meta.gps.coord_format() if meta.gps else "no GPS")

What we took from ExifTool (and improved)

ExifTool feature	Authentica equivalent
exiftool FILE — read all metadata	authentica meta FILE
EXIF: Make, Model, GPS, Aperture, ISO…	MetadataReader — full EXIF + composite
GPS decimal + deg/min/sec formatting (-c)	gps.coord_format("decimal"/"dms")
IPTC: Creator, Keywords, Caption	Parsed from APP13 IRB
XMP: Dublin Core, photoshop:, xmpRights:	Parsed from APP1/iTXt
ID3 tags (MP3)	meta.id3["Title"], ["Artist"]…
QuickTime/MP4 atoms	meta.quicktime["Title"]…
ICC color profile	meta.icc["ProfileDescription"]
MD5Sum, SHA256Sum composite tags	meta.md5, meta.sha256
Composite: Aperture, ShutterSpeed, LV	meta.composite["Aperture"] etc.
exiftool -diff FILE1 FILE2	diff_metadata(a, b)
exiftool -r -ext jpg DIR	BatchScanner(extensions={".jpg"}, recurse=True)
exiftool -csv DIR	results_to_csv(results)
exiftool -ThumbnailImage -b FILE	extract_thumbnail(file)
Cross-platform (Perl+DLLs on Windows)	Pure Python — works on Linux/macOS/Windows
-ver -v platform info	authentica version --verbose