Dynamic Image Encryption

Research-oriented Python implementation of a dynamic byte-level encryption algorithm using modular addition, modular subtraction, XOR and circular 8-bit rotation.

For each byte:

S_i = K_i mod 4

Then:

S=0 -> C=(P+K) mod 256
S=1 -> C=(P-K) mod 256
S=2 -> C=P XOR K
S=3 -> C=ROL(P,K mod 8)

Decryption applies the corresponding inverse operation.

Security note

This package is intended for research, experimentation and academic evaluation. It is not a replacement for established authenticated encryption schemes such as AES-GCM. No authentication/integrity mechanism is provided, and the key has the same length as the encrypted byte sequence.

Install

pip install "dynamic-image-encryption[all]"

Byte API

from image_encryption import encrypt, decrypt

ciphertext, key = encrypt(b"Hello")
plaintext = decrypt(ciphertext, key)

assert plaintext == b"Hello"

Image API

from image_encryption import encrypt_image, decrypt_image, save_key

key = encrypt_image("input.png", "encrypted.ienc")
save_key(key, "image.key")
decrypt_image("encrypted.ienc", key, "decrypted.png")

The image API works on decoded pixel bytes. Native Pillow modes are L, RGB and RGBA; other modes are converted to RGB. The decrypted conventional image is written as PNG.

NIfTI API

NIfTI voxel values are not reduced modulo 256. The raw bytes representing each voxel are encrypted. Thus an int16 voxel such as 7899 is encrypted as its two dtype/endianness-dependent bytes.

from image_encryption import encrypt_nifti, decrypt_nifti, save_key

key = encrypt_nifti("brain.nii.gz", "brain.ienc")
save_key(key, "brain.key")
decrypt_nifti("brain.ienc", key, "brain.decrypted.nii.gz")

The implementation stores the raw voxel dtype/shape, affine, NIfTI header, extensions and scaling information needed for reconstruction.

Tests

pip install -e ".[all,dev]"
pytest -q

Build

Change the PyPI name in pyproject.toml if the chosen name is already registered.

python -m build
python -m twine check dist/*
python -m twine upload --repository testpypi dist/*
python -m twine upload dist/*

Structure

image-encryption/
├── pyproject.toml
├── README.md
├── LICENSE
├── .gitignore
├── src/image_encryption/
│   ├── __init__.py
│   ├── core.py
│   ├── key.py
│   ├── operations.py
│   ├── container.py
│   ├── image.py
│   ├── nifti.py
│   └── exceptions.py
├── tests/
└── examples/

License

MIT.