lhe

Python library supporting level-4 homomorphic encryption, implemented as lifted ElGamal (level-2 HE) on BN254 and "boost" it using the Catalano-Fiore transformation.

Installation and Usage

This library is available as a package on PyPI:

python -m pip install lhe

The library can be imported in the usual way:

from lhe import *

The library exports everything needed to perform level-4 homomorphic encryption:

>>> from lhe import keygen, encrypt, decrypt

# A secret key is given to recipient and its corresponding public key is given to contrubutors.
>>> sk, pk = keygen()

# Contributors encrypt their data using that very same public key they have recieved.
>>> ct1 = encrypt(pk, 1)
>>> ct2 = encrypt(pk, 2)
>>> ct3 = encrypt(pk, 96)
>>> ct4 = encrypt(pk, 200)

# Compute party operates on those contributed ciphertexts.
>>> ct5 = (ct1 + ct2) * (ct3 + ct4)

# The recipient of the computation decrypts the resulting ciphertext of the computation.
>>> pt = decrypt(sk, ct5)

# Assuming the result is not too large of a number, it is resolved exactly.
>>> int(pt)
888

>>> from lhe.advanced import *
>>> sk1, pk1 = keygen1()
>>> sk2, pk2 = keygen2()
>>>
>>> ct1 = encrypt1(pk1, 3)
>>> ct2 = encrypt2(pk2, 222)
>>>
>>> ct3 = multiply(ct1, ct2)
>>>
>>> print("This may take a bit of time for large plaintexts...")
This may take a bit of time for large plaintexts...
>>>
>>> pt = decryptGT(ct3, sk1, sk2)
>>>
>>> print(pt)
666

Development

All installation and development dependencies are managed using setuptools and are fully specified in setup.py. The extras_require parameter is used to specify optional requirements for various development tasks. This makes it possible to specify additional options (such as docs, lint, and so on) when performing installation using pip:

python -m pip install .[docs,lint]

Documentation

The documentation can be generated automatically from the source files using Sphinx:

python -m pip install .[docs]
cd docs
sphinx-apidoc -f -E --templatedir=_templates -o _source .. ../setup.py && make html

Testing and Conventions

All unit tests are executed and their coverage is measured when using pytest (see setup.cfg for configuration details):

python -m pip install .[test]
python -m pytest

Alternatively, all unit tests are included in the module itself and can be executed using doctest:

python lhe/lhe.py -v

Style conventions are enforced using Pylint:

python -m pip install .[lint]
python -m pylint lhe

Contributions

In order to contribute to the source code, open an issue or submit a pull request on the GitHub page for this library.

Versioning

Beginning with version 0.1.0, the version number format for this library and the changes to the library associated with version number increments conform with Semantic Versioning 2.0.0.

Publishing

This library can be published as a package on PyPI by a package maintainer. First, install the dependencies required for packaging and publishing:

python -m pip install .[publish]

Remove any old build/distribution files. Then, package the source into a distribution archive using the wheel package:

rm -rf dist *.egg-info
python setup.py clean
python setup.py sdist bdist_wheel

Finally, increment the version and upload the package distribution archive to PyPI using the twine package:

python -m twine upload dist/*