Pixseal 0.2.0

Encrypted Image Watermark Injector / Validator

Pixseal

Prove what you published — and what you didn’t.

Pixseal is a Python-based image integrity and authenticity verification tool designed to detect whether an image has been modified since signing.

Pixseal embeds a cryptographically verifiable integrity seal into an image in an invisible manner. During verification, any modification — including editing, filtering, cropping, resizing, re-encoding — will cause verification to immediately fail.

If even a single pixel is altered after signing, Pixseal will detect it.

Pixseal is not a visual watermarking or branding tool.
The watermark exists solely as a means to achieve strict, deterministic image tamper detection. Pixseal prioritizes tamper sensitivity over robustness against intentional adversarial manipulation.

• GitHub: https://github.com/kyj9447/Pixseal
• Changelog: https://github.com/kyj9447/Pixseal/blob/main/CHANGELOG.md

Features

• Image Integrity Verification

  • Cryptographically proves that an image remains in its original, unmodified state
  • Detects single-pixel changes with deterministic verification results

• Tamper Detection

  • Detects all forms of image modification, including:
    • editing
    • filters and color adjustments
    • cropping and resizing
    • re-encoding and recompression
    • pixel-level changes

• Invisible Integrity Seal

  • Embeds verification data without any visible watermark
  • Preserves the original visual appearance of the image

• RSA-Based Encryption (Optional)

  • Supports RSA public/private key encryption for embedded verification data
  • Allows separation of signing and verification roles

• Verification & Extraction

  • Payloads may be partially or fully extractable even after modification
  • Automatically fails verification when tampering is detected

• Fully Local & Offline

  • No external servers or network dependencies
  • Pure Python implementation

• Lossless Format Support

  • Supports PNG and BMP (24-bit) images
  • Lossy formats (e.g., JPEG, WebP) are intentionally excluded to preserve integrity guarantees

Installation

pip install Pixseal
# or for local development
pip install -e ./pip_package

Python 3.8+ is required. The only runtime dependency is cryptography>=41.0.0.

Building from source

Cloning the repository and running the CLI/tests requires the Cython extension (Pixseal.simpleImage_ext) to be compiled. Wheels published to PyPI already bundle the compiled module, but a local checkout must be built manually:

git clone https://github.com/kyj9447/Pixseal.git
cd Pixseal
python3 -m pip install -r requirements.txt
./build.sh

Even after running python3 -m pip install -r requirements.txt you still need a working C toolchain (gcc) and the Python development headers exposed via python3-config; these come from your OS packages, not pip.

cd Pixseal
# optional: choose backend for testing (python fallback available)
./build.sh  # regenerates the C extension and runs `python -m build`

build.sh invokes Cython and gcc (via python3-config) before producing the wheel/sdist artifacts. Ensure cython, build, and a working C toolchain are installed. If you skip this step, Pixseal falls back to the pure Python implementation, which works but is significantly slower.

Usage

Sign an image

from Pixseal import signImage

result = signImage(
    imageInput="original.png",  # accepts a file path or raw PNG/BMP bytes
    hiddenString="!Validation:[e-mail]",
    publicKeyPath="RSA/public_key.pem",  # omit for plain-text embedding
)
result.save("signed_original.png")

• The payload is looped if it runs out before the image ends, so even small files carry the full sentinel/payload/end pattern.
• When publicKeyPath is omitted, the payload remains plain text.

Validate and (optionally) decrypt

from Pixseal import validateImage

report = validateImage(
    imageInput="signed_original.png",  # accepts a file path or raw PNG/BMP bytes
    privKeyPath="RSA/private_key.pem",  # omit for plain-text payloads
)

print(report["extractedString1"])
print(report["validationReport"])

validateImage returns:

{
    "extractedString1": "<payload or encrypted blob>",
    "extractedString2": "<truncated payload or encrypted blob>",
    "validationReport": {
        "arrayLength": 4,
        "lengthCheck": True,
        "startCheck": True,
        "endCheck": True,
        "isDecrypted": True,
        "tailCheckResult": True,
        "verdict": True,
        # decryptSkipMessage when a decrypt request was skipped
    }
}

CLI demo script

python testRun.py offers an interactive flow:

1. Choose 1 to sign an image. It reads original.png, asks for a payload (default !Validation:[e-mail]), optionally encrypts with RSA/public_key.pem, and writes signed_<name>.png.
2. Choose 2 to validate. It reads signed_original.png, optionally decrypts with RSA/private_key.pem, and prints both the extracted string and verdict.
3. Choose 3 to benchmark performance. It reads original.png, encrypts it with RSA/public_key.pem, and writes signed_original.png, printing the elapsed signing time. Then it reads signed_original.png, performs extraction/decryption/validation, and prints the elapsed validation time along with the total elapsed time.
4. Choose 4 to test signing and validation with file-path input option.
5. Choose 5 to test signing and validation with byte-stream input option.
6. Choose 6 to run the optional line-profiler demo. It benchmarks signImage and validateImage, printing per-line timings when the script is executed through kernprof.

Option 6 requires the optional dependency line_profiler and must be run via kernprof -l testRun.py so that builtins.profile is provided. Without line_profiler installed the script will continue to work, but the profiling option will display an informative message instead of running.

Key management

Generate a test RSA pair (PKCS#8) with OpenSSL:

openssl genpkey -algorithm RSA -out RSA/private_key.pem -pkeyopt rsa_keygen_bits:2048
openssl rsa -pubout -in RSA/private_key.pem -out RSA/public_key.pem

Point publicKeyPath / privKeyPath to these files.

API reference

Function	Description
signImage(imageInput, hiddenString, publicKeyPath=None)	Loads a PNG/BMP from a filesystem path or raw bytes, injects hiddenString plus sentinels, encrypting each chunk when publicKeyPath is provided. Returns a SimpleImage that you can save() or saveBmp().
validateImage(imageInput, privKeyPath=None)	Reads the hidden bit stream from a path or raw bytes, splits by newlines, deduplicates, optionally decrypts each chunk (Base64 indicates ciphertext), and returns the payload plus a validation report.

Examples

Original	Signed (!Validation:[e-mail])

Validation output excerpt:

[Validate] verdict: True
[Validate] extracted string: !Validation:[e-mail]
[Validate] decrypted with private key: RSA/private_key.pem

Validation Report

{'extractedString1': '!Validation:[e-mail]',
 'extractedString2': 'DMnWAzbd6NFycGAxcPkzzmGjL33WXovG...',
 'validationReport': {'arrayLength': 4,
                      'endCheck': True,
                      'isDecrypted': True,
                      'lengthCheck': True,
                      'startCheck': True,
                      'tailCheckResult': True,
                      'verdict': True}}

(When encrypted, each line appears as Base64 until decrypted with the RSA private key.)

Corrupted after signing

Validation output excerpt:

...
string argument should contain only ASCII characters
string argument should contain only ASCII characters
string argument should contain only ASCII characters
[Validate] verdict: False
[Validate] extracted string: !Validation:[e-mail]
[Validate] decrypted with private key: RSA/private_key.pem

Validation Report

{'extractedString1': '!Validation:[e-mail]',
 'extractedString2': 'hh78IWEsRgfTWMw3Rg02hTnCdErjx0O4...',
 'validationReport': {'arrayLength': 400,
                      'decryptSkipMessage': 'Skip decrypt: payload was plain '
                                            'or corrupted text despite decrypt '
                                            'request.',
                      'endCheck': True,
                      'isDecrypted': True,
                      'lengthCheck': False,
                      'startCheck': True,
                      'tailCheckResult': 'Not Required',
                      'verdict': False}}

Related projects

https://github.com/kyj9447/imageSignerCamera

• Mobile camera that signs images on capture:
• Server-side validator that decrypts and verifies payloads.