[tor-talk] my tor connection always timed out these days

Zhen Ling lingzhen1982 at gmail.com
Wed Apr 11 21:03:43 UTC 2012


According to the recent research of [1], I think it is useless to obtain 
the new bridges that does not support Obfsproxy [2] in China. Even if 
the Chinese users derive the new bridges which are not blocked in China, 
once the bridges are used by them, these bridges will be promptly 
discovered by GFC based on the protocol-level bridge discovery approach 
and then blocked. Therefore, currently, in order to effectively connect 
to the Tor network in China, the Chinese users should use the Obfsproxy 
to obfuscate the specific feature of the TLS protocol used by Tor. Since 
SkypeMorph [3] is not widely deployed, Obfsproxy is the only tool that 
we can use.

However, how do people in China retrieve the Obfsproxy supported 
bridges? Still obtain them via emails or https? [1] indicates that the 
13 hard-coded obfsproxy bridges in the official obfsproxy bundle have 
been already blocked.

[1] http://www.cs.kau.se/philwint/static/gfc/
[2] https://www.torproject.org/projects/obfsproxy.html.en
[3] http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf

On 11/04/2012 10:48 AM, Sam Whited wrote:
> Looks like about 80% of bridge relays are blocked from China these
> days (via the March 2012 progress report:
> https://blog.torproject.org/blog/march-2012-progress-report)
> Quote:
> "We developed a tool for scans of bridge lists which attempts to
>      either open a simple TCP connection to the bridge’s OR port or that
>      will perform a full Tor handshake to the bridge. We tested the
>      scanner by running a scan from Germany,
>      <https://trac.torproject.org/projects/tor/ticket/5028#comment:35>
>      and comparing results to bridge reachability information obtained
>      from the bridge authority in The Netherlands. We also performed a
>      scan from China,
>      <https://trac.torproject.org/projects/tor/ticket/5028#comment:45>,
>      and found that over 80% of bridges were unreachable. We compared
>      active scan results to passive usage statistics,
>      <https://trac.torproject.org/projects/tor/ticket/5028#comment:48>,
>      and confirmed that bridges that were found as unreachable in the
>      scan also reported significantly fewer connections from China than
>      other bridges."
> If you can't make a TCP connection to your bridge addresses, you may
> need to just keep requesting more until it works.
> —Sam
> On Wed, Apr 11, 2012 at 08:34, 季洪明<zeus2615 at gmail.com>  wrote:
>> This is a Chinese user
>> I added some new bridges, but that does not make it better.
>> My message log shows it always stuck at 80%
>> Anyone help?
>> thanks
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