Re: [tor-relays] Help the Tor Project by running a fast unpublished bridge

[Philipp Winter <identity.function@xxxxxxxxx>]

Hi Loz,

On Wed, Aug 15, 2012 at 11:00:11PM +0800, Lorenz Kirchner wrote:
>> I guess, that would require a modification of the path selection on the
>> clients
>> side. Usually, Tor clients randomly pick relays weighted by bandwidth.
>> Unless
>> the Chinese relays would provide an enormous amount of bandwidth, they
>> would
>> barely get selected by clients which leads to a poor user experience.
>
> well compared to now the experience would be better, eventually the reachable
> Chinese relays would connect it just might take a while on first startup

Yes, assuming the users would not give up out of frustration before :-) We can
actually do the math: According to [0], at the moment the Tor network has an
advertised bandwidth of 3000 MiB/s. Let's assume that all Chinese relays would
account for 30 MiB/s. Even then, the probability of a Chinese relay being
selected as first hop is only 30/3000 = 0.01 = 1%!

>> Perhaps it's better to focus on improved bridge distribution strategies [0]
>> and
>> hard-to-block transport protocols [1]. Also, that would be a universal
>> solution
>> which would also help in other countries and not a specific - and probably
>> hard
>> to maintain - Chinese-only solution.
>
> I think the solution is not a Chinese only solution as it would work anywhere
> where censorship actually exists

Only if you assume that the censor is always having a hard time censoring
content within its own borders. That might hold more-or-less true for China but
not everywhere else, right? For example, what about the networks of a company or
a small organization?

>> I guess, the firewall operators would notice that quite soon when Chinese
>> relays
>> would start popping up in the consensus or am I missing something here? And
>> as
>> soon as something is in the consensus, it's particularly easy to block.
>
> I am not sure how it works but I have a feeling that the firewall operators
> have difficulties in blocking hosts inside their networks 

That might be due to the fact that a lot of filtering (but not all of it) is
going on in border ASes. There even is a research paper about that if you are
interested [1].

However, there still remains a legal problem! You will have a hard time hiding
the fact that you are operating a relay within China. And if this turns out to
be a viable strategy, even more so. I suppose it wouldn't be too hard for the
government to simply confiscate or shut down Chinese relays?

After all, I agree with you that it's an interesting strategy which would tackle
the problem from a new angle and I would love to learn more about it. I just
believe that right now we should spend the limited resources we have on bridge
distribution and pluggable transports. It would surely be worth an experiment,
though!


Philipp

[0] https://metrics.torproject.org/network.html#bandwidth
[1] www.eecs.umich.edu/~zmao/Papers/china-censorship-pam11.pdf
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