X3DH 1.0.1

A Python implementation of the Extended Triple Diffie-Hellman key agreement protocol.

python-x3dh

A Python implementation of the Extended Triple Diffie-Hellman key agreement protocol.

Installation

python-x3dh depends on two system libraries, libxeddsa>=2,<3 and libsodium.

Install the latest release using pip (pip install X3DH) or manually from source by running pip install . (preferred) or python setup.py install in the cloned repository. The installation requires libsodium and the Python development headers to be installed. If a locally installed version of libxeddsa is available, python-xeddsa (a dependency of python-x3dh) tries to use that. Otherwise it uses prebuilt binaries of the library, which are available for Linux, MacOS and Windows on the amd64 architecture, and potentially for MacOS arm64 too. Set the LIBXEDDSA_FORCE_LOCAL environment variable to forbid the usage of prebuilt binaries.

Differences to the Specification

In the X3DH specification, the identity key is a Curve25519/Curve448 key and XEdDSA is used to create signatures with it. This library does not support Curve448, however, it supports Ed25519 in addition to Curve25519. You can choose whether the public part of the identity key in the bundle is transferred as Curve25519 or Ed25519. Refer to the documentation for details.

Testing, Type Checks and Linting

python-x3dh uses pytest as its testing framework, mypy for static type checks and both pylint and Flake8 for linting. All tests/checks can be run locally with the following commands:

$ pip install --upgrade pytest pytest-asyncio pytest-cov mypy pylint flake8
$ mypy --strict x3dh/ setup.py tests/
$ pylint x3dh/ setup.py tests/
$ flake8 x3dh/ setup.py tests/
$ pytest --cov=x3dh --cov-report term-missing:skip-covered

Documentation

View the documentation on readthedocs.io or build it locally, which requires the Python packages listed in docs/requirements.txt. With all dependencies installed, run make html in the docs/ directory. You can find the generated documentation in docs/_build/html/.