[messaging] WhatsApp & OWS team up

[Mike Hearn]

https://whispersystems.org/blog/whatsapp/

Huge, massive congratulations to Moxie and the team - this sort of
mainstream success is inspiring. I'd been hoping for a long time that once
TextSecure showed you could build a secure messenger with production
quality usability, Facebook / WhatsApp might pick it up, and today my dream
came true :)

This adds colour to Moxie's statement that he'd really like to avoid
hitting disk on the messaging path. I was a bit surprised this came up in
the context of TextSecure which cannot be hugely busy, but at WhatsApp
scale, that constraint is not at all surprising!

A bit of background for people in the USA who might not realise the
significance of this:   WhatsApp has more or less replaced SMS outside of
North America. It's got a de-facto monopoly on text messaging services.
When they say this is the biggest deployment of end to end crypto in
history, they are not exaggerating. It's harder to be bigger than this.

So what's next? I guess OWS and WhatsApp will be busy finishing off this
gigantic task for the forseeable future; i.e. adding to the rest of their
clients, covering all features, perhaps doing Signal/RedPhone style VoIP
and so on.

I can see a couple of directions to go now:

   1. Cracking the usable key verification problem. This move brings
   WhatsApp to the same level of security as iMessage (or better, given the
   forward security), but WhatsApp/Facebook could still do a switcheroo on
   people's keys. TextSecure never really figured this out IMO - it still
   expects people to manually compare long strings of hex.

   2. Building a trustworthy binary auditing and distribution process, so
   people can be assured that they're using what they think they're using. I
   have some ideas on this and have been doing a bit of work on it myself for
   Lighthouse, which features a threshold signature based auto update system.
   But the bulk of this work involves things like finding people who can be
   trusted to audit the source code in a variety of jurisdictions, making the
   builds reproducible, and finding a way to make the platform auto update
   mechanisms thresholded. I have some threshold RSA code I was able to
   extract from some academics a year or two ago that should in theory be
   compatible with Android, but I never tested it.

It will be interesting to see what the political ramifications of this are.
WhatsApp should now be pretty close to intercept-proof for all governments
bar the USA. Given its ubiquity and complete centralisation inside
California, I suspect this will result in all kinds of interesting jockying
as different countries try to get lawful intercept capabilities to it (by
switching keys, I guess).
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