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Python port of libsignal-protocol-java

Project description

libsignal-python
========
Signal encryption library for Python.

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About
--------
This is a python port of [libsignal-protocol-java](https://github.com/WhisperSystems/libaxolotl-android)
originally written by [Moxie Marlinspike](https://github.com/moxie0)

Compare with
[libsignal-protocol-php](https://github.com/albert-chin/libsignal-protocol-php)
forked from
[libaxolotl-php](https://github.com/mgp25/libaxolotl-php),
which is a php port.

Overview from original author's:

> This is a ratcheting forward secrecy protocol that works in synchronous
> and asynchronous messaging environments. The protocol overview is available
> [here](https://github.com/trevp/axolotl/wiki), and the details of the wire
> format are available [here](https://github.com/trevp/axolotl/wiki).

Read rest of of details [here](https://github.com/WhisperSystems/libaxolotl-android/blob/master/README.md).


Installation
--------
The library has some dependencies which are automatically pulled and installed
if you use the instructions below for your OS

- [protobuf 3.6+](https://github.com/google/protobuf/)
- [cryptography](https://cryptography.io)
- [python-axolotl-curve25519](https://github.com/tgalal/python-axolotl-curve25519)

## Linux

You need to have python headers installed, usually through installing a package called `python-dev`, then as superuser run:
```
python setup.py install
```

## Mac

I don't have mac to test. Send me instructions or a MacBook.

## Windows

- Install [mingw](http://www.mingw.org/) compiler
- Add mingw to your PATH
- In PYTHONPATH\Lib\distutils create a file called distutils.cfg and add these lines:

```
[build]
compiler=mingw32
```

- Install gcc: ```mingw-get.exe install gcc```
- Install [zlib](http://www.zlib.net/)
- ```python setup.py install```


Usage
--------
This python port is done in an almost 1:1 mapping to the original java code.
Therefore any original documentation for the java code can be easily mapped
and used with this python port.

## Install time

At install time, a libaxolotl client needs to generate its identity keys, registration id, and
prekeys.

```python
identityKeyPair = KeyHelper.generateIdentityKeyPair()
registrationId = KeyHelper.generateRegistrationId()
preKeys = KeyHelper.generatePreKeys(startId, 100)
lastResortKey = KeyHelper.generateLastResortKey()
signedPreKey = KeyHelper.generateSignedPreKey(identityKeyPair, 5)

#Store identityKeyPair somewhere durable and safe.
#Store registrationId somewhere durable and safe.

#Store preKeys in PreKeyStore.
#Store signed prekey in SignedPreKeyStore.
```

## Building a session

A libaxolotl client needs to implement four interfaces: IdentityKeyStore, PreKeyStore,
SignedPreKeyStore, and SessionStore. These will manage loading and storing of identity,
prekeys, signed prekeys, and session state.

Once those are implemented, building a session is fairly straightforward:

```python
sessionStore = MySessionStore()
preKeyStore = MyPreKeyStore()
signedPreKeyStore = MySignedPreKeyStore()
identityStore = MyIdentityKeyStore()

# Instantiate a SessionBuilder for a remote recipientId + deviceId tuple.
sessionBuilder = SessionBuilder(sessionStore, preKeyStore, signedPreKeyStore,
identityStore, recipientId, deviceId)

# Build a session with a PreKey retrieved from the server.
sessionBuilder.process(retrievedPreKey)

sessionCipher = SessionCipher(sessionStore, recipientId, deviceId)
message = sessionCipher.encrypt("Hello world!")

deliver(message.serialize())
```


Examples
--------
python-axolotl is actively used in [yowsup](https://github.com/tgalal/yowsup) to
support the new end to end encryption in WhatsApp


License
--------
Licensed under the GPLv3: http://www.gnu.org/licenses/gpl-3.0.html

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