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Re: Re: problem with bridges and a suggestion

dear andrew,

thanks a lot for your prompt reply.

as to your question:
Can you send debug logs to tor-assistants@xxxxxxxxxxxxxx with what
happens when your client tries to connect to the bridges?

my answer:
sorry, I'm not familiar with TOR development, could you kindly tell me which file or files the debug logs are in?

as to your comment:
This is unlikely.  In our experience, they are merely blocking IP:Port combinations.

my answer:
I know some developers of china's blocking projects, so I know that they have more methods than that.
first, the so-called "static blocking" method include both mere IP mode and IP:port combination mode;
second, the so-called "dynamic blocking" mothod can break tcp connection upon traffic fingerprints.

hope I can help.
	 
frank
2010-05-26

-------------------------------------------------------------
åääïandrew
åéææï2010-05-25 19:52:05
æääïor-talk
æéï
äéïRe: problem with bridges and a suggestion

On Tue, May 25, 2010 at 05:18:44PM +0800, for.tor.bridge@xxxxxxxxx wrote 1.3K bytes in 36 lines about:
: china is blockingÂTORÂ more and more strict,
: I can'tÂestablish a TOR circuitÂeven IÂupdated bridges in config file
: of torrc with info retrievedÂfrom https://bridges.torproject.orgÂand
: email replies from bridges@xxxxxxxxxxxxxxx

Correct.  We are aware of this.

: this morning,ÂI got some new bridges through a hidden https proxy and
: established a TOR circuit, but after some time, I lost the connection
: and couldn't establish a TOR circuit any more.

Can you send debug logs to tor-assistants@xxxxxxxxxxxxxx with what
happens when your client tries to connect to the bridges?

: from my knowledge to china's blocking methods, I believe they found my
: newly got bridges through network traffic protocol analysis, and
: blocked them.

This is unlikely.  In our experience, they are merely blocking IP:Port
combinations.

: use a general protocol for TOR clients to interact with bridges, so
: that they can't distinguish the traffic between TOR clients and
: bridges,
: so that they can't find new bridges got through private ways.

Tor traffic through bridges vs. public relays is the same.  There is not
a special "bridge connection".  See
https://www.torproject.org/faq#RelayOrBridge, also that text needs to be
updated to reflect China's uniqueness in filtering Tor public relays.

: the general protocol could be https which is encryption protected;

It is already.  What may be unique is we start the connection with a TLS
renegotiation.  This is probably starting to stand out as unique now
that OpenSSL decided to everyone used renegotiation incorrectly and
almost all operating systems have erroneously disabled this
functionality by default.  See
https://www.torproject.org/faq#KeyManagement

: the general protocol could be plain http, if you can encode its
: content dynamically and privately, and don't make it display any
: fingerprints.

Then someone can read your traffic.  Hiding in plain sight sounds good
on paper, but doesn't stand up to academic research, so far.  See
https://trac.torproject.org/projects/tor/wiki/TheOnionRouter/TorFAQ#YoushouldusesteganographytohideTortraffic.

-- 
Andrew Lewman
The Tor Project
pgp 0x31B0974B

Website: https://www.torproject.org/
Blog: https://blog.torproject.org/
Identi.ca: torproject
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