Implement encrypted communication via the Axolotl protocol/library

[Chaos99]

Fork of #Issue36 "Off-the-Record (OTR) Messaging"

Citing user @taoeffect in his comment to the original issue:

Problem with OTR is that it only works while both users are online.

I recommend using Axolotl instead, developed by Open WhisperSystems of TextSecure/Signal fame. It's like OTR but it supports secure asynchronous messaging, which is important because it's rare that everyone is online all the time. :)

There are lots of Axolotl libraries out there, available for both iOS, Android, and Web.

https://github.com/WhisperSystems/Signal-iOS
https://github.com/WhisperSystems/TextSecure-Browser/tree/libaxolotl/
https://github.com/WhisperSystems/TextSecure
https://github.com/joebandenburg/libaxolotl-javascript
https://github.com/joebandenburg/libaxolotl-crypto-web

WhisperSystems have shown in their beta desktop app that multi-user-multi-device chat with history is possible.

Thread model is a compromised server (admin with full read/write access) before, during or after the conversation. (Which Axolotl matches to my knowledge.) Authenticity of the client application needs to be secured by verifying signatures over a side channel, availability from multiple sources or relying on a trusted provider.

[engelgabriel]

This would be awesome!

[mitar]

So the Axolotl file transfer is directly between peers without an intermediate server? So they have to be both online at that moment?

[xenithorb]

+1

[engelgabriel]

Hi guys, we will merge this PR that covers adding a new protocol for encryption #10094