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On 2013-05-28 4:42 PM, adrelanos wrote:
<br>
<blockquote type="cite" style="color: #000000;">The more pluggable
transports, the better.
<br>
Maybe if there are enough transports, the other side just gives
up.
<br>
</blockquote>
<br>
<br>
My interest is piqued by this statement and similar sounding ones
that I hear, and myself also think, when talking about censorship.
<br>
I suspect that if certain information leakage events (ILE) are
important for the censor then I don't think giving up is an option,
even if it means doing the hard(?) task of blocking all the
pluggable transports. Of course this is all conjecture---I don't
know the censor---which brings me to my main point:
<br>
<br>
It is important that we have a model of which censor we are wanting
to defeat (or at least annoy). I don't mean every censor or every
use case, just the one we are currently discussing. Also, we can
have different descriptions of the same censor depending on the
situation. The same censor can bring to bear very different tools
depending on if the users are being annoying enough, or if
ultimately the problem can be dealt with by non-Internet means. This
also allows us to talk about the same censor and produce different
censorship solutions depending on our goals and the censorship
conditions that apply. We can through our actions (like becoming
popular) shift the censorship context and thus have to reevaluate
our solution.
<br>
<br>
I know that it is fiendishly difficult to get correct but it would
help the discussion if we knew exactly what we're up against, at
least in qualitative terms.
<br>
<br>
My attempt from what I think we're talking about, please correct/add
to this where I err:
<br>
<br>
Circumvention strategies:
<br>
0. Collateral damage and obfuscation.
<br>
<br>
Censor Capabilities:
<br>
1. View all traffic coming in and out of a network (most likely has
visibility of all AS and IX level traffic). We'll call this the
visibility bubble.
<br>
2. Can manipulate (add, delete, change) said traffic in time and
data dimensions.
<br>
<br>
Motivations:
<br>
3. Block <b class="moz-txt-star"><span class="moz-txt-tag">*</span>all<span
class="moz-txt-tag">*</span></b> information leakage events.
This means if even one ILE occurs the circumventor wins.
<br>
4. Limit collateral damage but some is acceptable.
<br>
<br>
Censorship Target:
<br>
5. General user population (G) within the visibility of the bubble.
<br>
6. Circumventor population (Cr) in visibility bubble.
<br>
7. Cr/G << 1; the incidence rate (R).
<br>
<br>
I think that this censor, while in a seemingly powerful position due
to 1 and 2, is in a difficult dilemma due to 3 and 4, especially if
7 is a small number.
<br>
Of course if we relax the condition of blocking <b
class="moz-txt-star"><span class="moz-txt-tag">*</span>all<span
class="moz-txt-tag">*</span></b> ILEs then the situation becomes
more favorable for the censor.
<br>
<br>
I hope that descriptions such as the above really help identify the
issues at hand helps focus on what is pertinent. I suspect that with
Tor being useful to a diverse user-base the censorship scenarios are
just as varied and the solutions (even within the plugabble
transport space) can be useful in ways we did not think of.
<br>
<br>
Cheers,
<br>
-mtee
<br>
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