[Standards] OTR

Carlo v. Loesch CvL at mail.symlynX.com
Tue Feb 3 11:52:41 UTC 2015


If you're interested in looking beyond the XMPP bowl there has been
very similar discussion in the post-XMPP "messaging" list:

https://moderncrypto.org/mail-archive/messaging/2015/001309.html
    "Multiple devices and key synchronization"

https://moderncrypto.org/mail-archive/messaging/2015/001354.html
    "Key rotation"

On Tue, Feb 03, 2015 at 11:07:40AM +0100, Winfried Tilanus wrote:
> https://github.com/winfried/XMPP-OTR

I think the XMPP/OTR/Tor combination is what people are using *today*
because you have to start somewhere and the other options (TorChat or
Retroshare via Tor) aren't as mature.

Yet I think the XMPP community should REALLY REALLY acknowledge
that the metadata issue IS more important than the forward secrecy
aspect and that applying a bit of Tor on the way to the server
is NOT a sufficient solution.

As George Danezis expressed it in his 31c3 presentation, social
graphs tent to be isomorphic. No matter how well you pseudonymize
your identity via Tor, the people you add to your roster are
going to be similar to the ones you already added to other social
graphs. The 2009 paper "de-anonymizing social networks" shows how
an attacker can correlate social graphs.

So if a five eyes state agency wants to know everyone's identities
on jabber.org or jabber.ccc.de, it either needs to obtain access 
to the server data base, or apply plenty of traffic shaping over 
a period of time, to extract that graph - then compare it to 
existing intelligence such as the Facebook, Twiter or e-mail
social network graphs.

In other words, no matter how much OTR and Tor we throw at it,
the fact that XMPP uses federated servers will always put our
metadata at risk. Federation has also failed us ideologically:
Each time a federated protocol becomes popular, cloud offerings 
turn out to be the most efficient, scalable and easy to adopt
for the masses. Thus federated protocols such as SMTP and XMPP
have been a slippery slope leading into centralized cloud dependency -
legitimizing platforms such as Gmail and G-Talk. Even Facebook Chat.

If you want to do the world some good, help us work on a distributed,
end-to-end encrypted and forward secret technology that builds upon
agnostic anonymizing relay nodes rather than federated servers. An
architecture that keeps the social graph completely on the devices
of the users rather than replicating it into the network infrastructure.

You may find this thread interesting. It discusses the possibilities
of implementing a one-to-many messaging system into the backbone of Tor:

https://lists.torproject.org/pipermail/tor-talk/2014-December/036251.html
    "Cryptographic social networking project"

Concluding, please use XMPP for things it is appropriate for... don't
try to do privacy with it. It's a battle we can't win.


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