[tor-talk] [ZS] Re: End-to-end correlation for fun and profit

Eugen Leitl eugen at leitl.org
Tue Aug 21 17:27:22 UTC 2012


----- Forwarded message from Bryce Lynch <virtualadept at gmail.com> -----

From: Bryce Lynch <virtualadept at gmail.com>
Date: Tue, 21 Aug 2012 13:08:52 -0400
To: zs-p2p at googlegroups.com
Cc: doctrinezero at googlegroups.com
Subject: [ZS] Re: [tor-talk] End-to-end correlation for fun and profit
Reply-To: doctrinezero at googlegroups.com

On Tue, Aug 21, 2012 at 3:39 AM, ZeroState.net <info at zerostate.net> wrote:

> This sounds like a potentially powerful anti-Tor method, if I
> understand correctly. Basically it's an inference method that treats
> the Tor network as a black box, right?
>
> Do we think this is a serious problem?

I don't know.

There isn't a whole lot we can do if entire ISPs are tapped (the Syria
problem) aside from avoid their network infrastructure entirely.
...
After sprinting through the Tor source code, I came across this
official documentation pertaining to how Tor chooses next nodes in a
circuit:

https://gitweb.torproject.org/torspec.git/blob/HEAD:/path-spec.txt#l184

Quote:
"We do not choose more than one router in a given /16 subnet (unless
EnforceDistinctSubnets is 0)."

This configuration setting defaults to 1/True.  Verified:
https://gitweb.torproject.org/tor.git/blob/49d150a9fad2cb8d3887af1e112b15365c11f4ba:/src/or/config.c#l2591
https://gitweb.torproject.org/tor.git/blob/49d150a9fad2cb8d3887af1e112b15365c11f4ba:/src/or/or.h#l2777
https://gitweb.torproject.org/tor.git/blob/49d150a9fad2cb8d3887af1e112b15365c11f4ba:/src/or/routerlist.c#l1350
https://gitweb.torproject.org/tor.git/blob/49d150a9fad2cb8d3887af1e112b15365c11f4ba:/src/or/routerlist.c#l1401

This claim sounds a little fishy to me, in this light.

-- 
The Doctor [412/724/301/703] [ZS]
https://drwho.virtadpt.net/
"I am everywhere."

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