additive 0.2.0

Data structure for representing additive secret shares of integers, designed for use within secure MPC protocol implementations.

Data structure for representing additive secret shares of integers, designed for use within secure multi-party computation (MPC) protocol implementations.

Purpose

This library provides a data structure and methods that make it possible work with n-out-of-n additive secret shares of integers within secure multi-party computation (MPC) protocol implementations. Secret shares of signed and unsigned integers can be represented using elements from finite fields, with support currently limited to fields having a power-of-two order.

Package Installation and Usage

The package is available on PyPI:

python -m pip install additive

The library can be imported in the usual ways:

import additive
from additive import *

Examples

This library makes it possible to concisely construct multiple secret shares from an integer:

>>> from additive import shares
>>> (a, b) = shares(123)
>>> (c, d) = shares(456)
>>> ((a + c) + (b + d)).to_int()
579

It is possible to specify the exponent in the order of the finite field used to represent secret shares, as well as whether the encoding of the integer should support signed integers:

>>> (s, t) = shares(-123, exponent=8, signed=True)
>>> (s + t).to_int()
-123

The number of shares can be specified explicitly (the default is two shares):

>>> (r, s, t) = shares(123, quantity=3)

The share data structure supports Python’s built-in addition operators in order to enable both operations on shares and concise reconstruction of values from a collection of secret shares:

>>> (r + s + t).to_int()
123
>>> sum([r, s, t]).to_int()
123

In addition, conversion methods for Base64 strings and bytes-like objects are included to support encoding and decoding of share objects:

>>> from additive import share
>>> share.from_base64('HgEA').to_bytes().hex()
'1e0100'
>>> [s.to_base64() for s in shares(123)]
['PvmKMG8=', 'PoJ1z5A=']

Documentation

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

cd docs
python -m pip install -r requirements.txt
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 nose (see setup.cfg for configuration details):

python -m pip install nose coverage
nosetests --cover-erase

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

python additive/additive.py -v

Style conventions are enforced using Pylint:

python -m pip install pylint
pylint additive

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

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.