Subject: Re: [Pearg] Research Group Last Call for "A Survey of Worldwide Censorship Techniques"

From: Joseph Lorenzo Hall <[email-masked]>
Date: Mon, 1 Jun 2020 11:14:24 +0000

The Tschantz SOK reviews empirical studies and findings about what censors have done in order to inform academic study of censorship circumvention, so quite useful for a this document (even if we don't go into the ongoing saga of the circumvention arms race).

--
Joseph Lorenzo Hall, Senior Vice President, Strong Internet
[email-masked] | +1-703-483-9504
internetsociety.org | @internetsociety
pgp: https://josephhall.org/gpg-key
3CA28D7B9F6DDBD34B1016075F86698740A9A871
________________________________
From: Pearg <[email-masked]> on behalf of David Oliver <[email-masked]>
Sent: Saturday, May 30, 2020 3:11:30 PM
To: Eliot Lear <lear=[email-masked]>
Cc: [email-masked] <[email-masked]>
Subject: Re: [Pearg] Research Group Last Call for "A Survey of Worldwide Censorship Techniques"

> Be a bit more explicit as to what the relevancies are.

I was actually wondering the opposite: Why *are* circumvention methods mentioned in this document?  Should I work on the assumption that "why" was hashed out in discussion of earlier drafts?

David

David M. Oliver | david@g<mailto:[email-masked]>uardianproject.info<http://uardianproject.info> | http://g<http://olivercoady.com>uardianproject.info<http://uardianproject.info> | @davidmoliver | +1 970 368 2366

On Sat, May 30, 2020 at 11:52 AM Eliot Lear <lear=[email-masked]<mailto:[email-masked]>> wrote:
Mallory,

I wanted to come back to something you wrote:

On 26 May 2020, at 19:04, Mallory Knodel <[email-masked]<mailto:[email-masked]>> wrote:

Because while there are indeed recognized legal, legitimate and proportional reasons why the rights to free expression and to access information should be violated, censorship measures should not be taken without careful consideration as it is a human rights matter.

Regardless of the terminology, it seems to me that there is another aspect that the document could capture that is related to the IETF.  In the introduction, the authors write:

   There is also a growing field of
   academic study of censorship circumvention (see the review article of
   [Tschantz-2016]), results from which we seek to make relevant here
   for protocol designers and implementers.

I wonder if it would be good to elaborate this.  Be a bit more explicit as to what the relevancies are.  Are these cautionary tales for instance, wherein some cases the use of the technology for censorship was not what the engineers had in mind?  How would you like engineers to evaluate technology tradeoffs?

This allows us to address one additional point that I’d suggest the RG to consider:  the document motivation could be strengthened.  Why is this document important?  Who is it relevant to?  This might also explain why there is no conclusion or desired next steps.  Good that they've enumerated various mechanisms.  Would they like the IETF to review those points with an eye toward avoiding inadvertent avenues to additional censorship?  What if anything would be good for PEARG to follow up?  I’m not suggesting many paragraphs, but one or two wouldn’t be out of line.

Eliot

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Pearg mailing list
[email-masked]<mailto:[email-masked]>
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---

From: Chelsea Komlo <[email-masked]>
Date: Tue, 2 Jun 2020 08:30:50 -0600

Hi Chris,

I have a couple meta points and a few specific points.

Overall, my strongest recommendation is threefold. First, I recommend
improving the document organization to clearly differentiate between a
specific censorship technique and corresponding methods to circumvent that
technique. Second, I suggest strengthening the review of current
circumvention techniques and their effectiveness to give an improved view
of the landscape and to prevent re-inventing the wheel, as the intended
audience is protocol designers. Third, I recommend differentiating between
the capabilities of mature censors like China, and weaker censors such as
those with only off-the-shelf tools.

Here is my discussion of these points in more detail.

=== Meta Points ===
- While I understand this draft to be purely informational, understanding
censorship today is incomplete without understanding existing censorship
circumvention techniques, and how effective these techniques are.
Critically, some of the most effective and safe censorship techniques are
"hanging by a thread" in terms of how much longer they will be available
(such as domain fronting), so understanding these weak areas is important
to understanding the sustainability of the current circumvention landscape.
I suggest adding at minimum a discussion of "Where are we today" regarding
circumvention.
- To go along with the above point,  providing a better review of existing
censorship circumvention techniques will help encourage building on
existing work, as opposed to re-inventing the wheel from first principles.
While perhaps this review should be a follow-up document, I strongly
encourage providing such a review, especially since the intended audience
is protocol designs.
- Within the draft itself, the discussion of censorship techniques is often
interwoven with circumvention methods. I suggest separating these concepts
out within each section. Instead of a "Tradeoffs" section, perhaps have
sections pertaining to "Cost to Implement to Censor", and "Techniques to
Circumvent", for improved clarity.
- One important point is that while China is an extremely powerful censor,
they are often in a class of their own. I encourage including a discussion
of something like "censor maturity" or the technical resources required to
implement different techniques. There is a bit of this discussion, but it
can be better standardized and applied to each technique. For example, IP
blacklisting is trivial and does not require significant infrastructure
(and many censors do this), but performing active probing to fingerprint
protocols and block them on the fly requires much more infrastructure and
planning (and is essentially only China, as I understand).

=== Specific Points ===
- DPI (deep packet inspection) is technically any kind of packet analysis
beyond IP address and port number- this concept can be better clarified.
Further, this technique is not specific to
- Clearly highlighting techniques that are thwarted by the use of TLS
versus techniques which can be performed even in spite of TLS usage would
also likely be helpful to readers.

Thanks,
Chelsea

On Wed, May 20, 2020 at 11:00 AM Christopher Wood <[email-masked]>
wrote:

> This is the research group last call for the "A Survey of Worldwide
> Censorship Techniques" (draft-irtf-pearg-censorship) draft available here:
>
>    https://datatracker.ietf.org/doc/draft-irtf-pearg-censorship/
>
> Please review the document and send your comments to the list by June 5,
> 2020. Feedback may also be sent to the GitHub repository located here:
>
>    https://github.com/IRTF-PEARG/rfc-censorship-tech
>
> Thanks,
> Chris, on behalf of the chairs
>
> --
> Pearg mailing list
> [email-masked]

-- 
Chelsea H. Komlo

---

From: Joseph Lorenzo Hall <[email-masked]>
Date: Tue, 2 Jun 2020 14:35:53 +0000

Thank you, Chelsea!

I have a ton of $dayjob responsibilities this week that make it difficult to respond quickly, so I think what I'll do is absorb this and other reviews and peel off github issues (discussion which I'll replicate or reference here) to deal with these later this week (and I'll pow-wow with chairs, e.g, Chris).

Very thankful for the many reviews and please don't let my inability to respond quickly stifle any discussion! best, Joe
________________________________
From: Pearg <[email-masked]> on behalf of Chelsea Komlo <[email-masked]>
Sent: Tuesday, June 2, 2020 10:30
To: Christopher Wood <[email-masked]>
Cc: [email-masked] <[email-masked]>
Subject: Re: [Pearg] Research Group Last Call for "A Survey of Worldwide Censorship Techniques"

Hi Chris,

Overall, my strongest recommendation is threefold. First, I recommend improving the document organization to clearly differentiate between a specific censorship technique and corresponding methods to circumvent that technique. Second, I suggest strengthening the review of current circumvention techniques and their effectiveness to give an improved view of the landscape and to prevent re-inventing the wheel, as the intended audience is protocol designers.. Third, I recommend differentiating between the capabilities of mature censors like China, and weaker censors such as those with only off-the-shelf tools.

=== Meta Points ===
- While I understand this draft to be purely informational, understanding censorship today is incomplete without understanding existing censorship circumvention techniques, and how effective these techniques are.. Critically, some of the most effective and safe censorship techniques are "hanging by a thread" in terms of how much longer they will be available (such as domain fronting), so understanding these weak areas is important to understanding the sustainability of the current circumvention landscape. I suggest adding at minimum a discussion of "Where are we today" regarding circumvention.
- To go along with the above point,  providing a better review of existing censorship circumvention techniques will help encourage building on existing work, as opposed to re-inventing the wheel from first principles. While perhaps this review should be a follow-up document, I strongly encourage providing such a review, especially since the intended audience is protocol designs.
- Within the draft itself, the discussion of censorship techniques is often interwoven with circumvention methods. I suggest separating these concepts out within each section. Instead of a "Tradeoffs" section, perhaps have sections pertaining to "Cost to Implement to Censor", and "Techniques to Circumvent", for improved clarity.
- One important point is that while China is an extremely powerful censor, they are often in a class of their own. I encourage including a discussion of something like "censor maturity" or the technical resources required to implement different techniques. There is a bit of this discussion, but it can be better standardized and applied to each technique. For example, IP blacklisting is trivial and does not require significant infrastructure (and many censors do this), but performing active probing to fingerprint protocols and block them on the fly requires much more infrastructure and planning (and is essentially only China, as I understand).

=== Specific Points ===
- DPI (deep packet inspection) is technically any kind of packet analysis beyond IP address and port number- this concept can be better clarified. Further, this technique is not specific to
- Clearly highlighting techniques that are thwarted by the use of TLS versus techniques which can be performed even in spite of TLS usage would also likely be helpful to readers.

Thanks,
Chelsea

On Wed, May 20, 2020 at 11:00 AM Christopher Wood <[email-masked]<mailto:[email-masked]>> wrote:
This is the research group last call for the "A Survey of Worldwide Censorship Techniques" (draft-irtf-pearg-censorship) draft available here:

Please review the document and send your comments to the list by June 5, 2020. Feedback may also be sent to the GitHub repository located here:

Thanks,

--
Chelsea H. Komlo

---

From: David Oliver <[email-masked]>
Date: Tue, 2 Jun 2020 10:59:45 -0400

Chelsea, thanks for this.

> First, I recommend improving the document organization to clearly
differentiate
>  between a specific censorship technique and corresponding methods to
circumvent that technique.

I'm still not understanding why - in a document defined to talk about
censorship techniques - we're talking about circumvention methods. I
believe it's particularly important to understand because, at least for the
techniques I'm familiar with, these methods work "above the stack", not "in
the stack" because we implementors can't have impact on "the stack"
itself.  IETF addresses "the stack" so, in theory at least, IETF could use
the understanding of censorship techniques to implement solutions there.
Why would we (implementors) be engaging with IETF if we do not seek new "in
the stack" methods of preventing censorship?

Thanks for any clarification that can be provided.

David Oliver
David M. Oliver | david@g <[email-masked]>uardianproject.info |
http://g <http://olivercoady.com>uardianproject.info | @davidmoliver | +1
970 368 2366

On Tue, Jun 2, 2020 at 10:31 AM Chelsea Komlo <[email-masked]>
wrote:

> audience is protocol designers.. Third, I recommend differentiating between
> circumvention techniques, and how effective these techniques are..
> - Within the draft itself, the discussion of censorship techniques is
> often interwoven with circumvention methods. I suggest separating these
> concepts out within each section. Instead of a "Tradeoffs" section, perhaps
> have sections pertaining to "Cost to Implement to Censor", and "Techniques
> to Circumvent", for improved clarity.

---

From: Chelsea Komlo <[email-masked]>
Date: Tue, 2 Jun 2020 11:14:55 -0600

Hi David,

> the stack" methods of preventing censorship?
While yes, IETF can certainly address censorship techniques "down the
stack", it is still critical to understand how existing circumvention
techniques have or have not been successful in order to design for the
future. There is a learning curve to understanding how to design for
censorship circumvention and I would hate to see all of the same mistakes
made that are already known to practitioners building circumvention tools
higher up in the stack.

So in short, let's avoid re-learning lessons that have already been learned
in this space.

Chelsea

---

From: Amelia Andersdotter <[email-masked]>
Date: Wed, 3 Jun 2020 12:57:57 +0200

On 2020-05-29 19:28, Eric Rescorla wrote:
> Document: draft-irtf-pearg-censorship-03.txt
>
> S 2.
>     We describe three elements of Internet censorship: prescription,
>     identification, and interference.  The document contains three major
>     sections, each corresponding to one of these elements.  Prescription
>     is the process by which censors determine what types of material they
>     should block, i.e., deciding to block a list of pornographic
>     websites.  Identification is the process by which censors classify
>     specific traffic to be blocked or impaired, i.e., blocking or
>     impairing all webpages containing "sex" in the title or traffic to
>     www.sex.example.  Interference is the process by which censors
>
> I'm not finding this distinction super clear. It seems to me like
> deciding to block www.sex.example and "impairing...traffic to
> www.sex.example" are pretty similar.

I felt like picking up on this: the difference between blocking and
impairing is that blocking would be definitive (content is rendered
inaccessible to end-node), while impairment would just mean, for
instance, downgraded in quality (content is made to run more slow or
without encryption, for instance). I do feel there is a point to keeping
that distinction.

It serves the purpose of highlighting that censorship may take more
subtle forms than outright bans on sensitive content.

best regards,

Amelia

---

From: Eric Rescorla <[email-masked]>
Date: Wed, 3 Jun 2020 05:52:50 -0700

> without encryption, for instance). I do feel there is a point to keeping

This was actually bad quoting on my part because the text actually
has "i.e., blocking or impairing...". My point is that "deciding to"
and "doing" seem pretty similar...

> subtle forms than outright bans on sensitive content.

I definitely agree.

best regards,

---

From: "Christopher Wood" <[email-masked]>
Date: Wed, 03 Jun 2020 09:15:23 -0700

Thanks for the review, Chelsea!

On Tue, Jun 2, 2020, at 7:30 AM, Chelsea Komlo wrote:
> specific censorship technique and corresponding methods to circumvent 
> that technique. Second, I suggest strengthening the review of current 
> circumvention techniques and their effectiveness to give an improved 
> view of the landscape and to prevent re-inventing the wheel, as the 
> intended audience is protocol designers. Third, I recommend 
> differentiating between the capabilities of mature censors like China, 
> and weaker censors such as those with only off-the-shelf tools. 
> 
> - While I understand this draft to be purely informational, 
> understanding censorship today is incomplete without understanding 
> existing censorship circumvention techniques, and how effective these 
> techniques are. Critically, some of the most effective and safe 
> censorship techniques are "hanging by a thread" in terms of how much 
> longer they will be available (such as domain fronting), so 
> understanding these weak areas is important to understanding the 
> sustainability of the current circumvention landscape. I suggest adding 
> at minimum a discussion of "Where are we today" regarding circumvention.
> - To go along with the above point, providing a better review of 
> existing censorship circumvention techniques will help encourage 
> building on existing work, as opposed to re-inventing the wheel from 
> first principles. While perhaps this review should be a follow-up 
> document, I strongly encourage providing such a review, especially 
> since the intended audience is protocol designs. 
> concepts out within each section. Instead of a "Tradeoffs" section, 
> perhaps have sections pertaining to "Cost to Implement to Censor", and 
> "Techniques to Circumvent", for improved clarity. 
> - One important point is that while China is an extremely powerful 
> censor, they are often in a class of their own. I encourage including a 
> discussion of something like "censor maturity" or the technical 
> resources required to implement different techniques. There is a bit of 
> this discussion, but it can be better standardized and applied to each 
> technique. For example, IP blacklisting is trivial and does not require 
> significant infrastructure (and many censors do this), but performing 
> active probing to fingerprint protocols and block them on the fly 
> requires much more infrastructure and planning (and is essentially only 
> China, as I understand). 
> 
> === Specific Points ===
> - DPI (deep packet inspection) is technically any kind of packet 
> analysis beyond IP address and port number- this concept can be better 
> clarified. Further, this technique is not specific to 
> versus techniques which can be performed even in spite of TLS usage 
> would also likely be helpful to readers. 
> 
> Thanks,
> Chelsea
> 
> On Wed, May 20, 2020 at 11:00 AM Christopher Wood <[email-masked]> wrote:

---

From: "Christopher Wood" <[email-masked]>
Date: Fri, 05 Jun 2020 16:34:08 -0700

This research group last call is complete. Thanks to everyone who contributed along the way!

Based on the feedback and reviews received thus far, the chairs think this document needs more work before moving ahead. We will follow up with Joe and the other authors to address all feedback in the coming weeks.

Best,

On Wed, May 20, 2020, at 9:59 AM, Christopher Wood wrote:
> Please review the document and send your comments to the list by June 
> 5, 2020. Feedback may also be sent to the GitHub repository located 
> here:
>

---

From: Joseph Lorenzo Hall <[email-masked]>
Date: Fri, 5 Jun 2020 23:36:28 +0000

Agreed! Thank you everyone, more to come

--
Joseph Lorenzo Hall, Senior Vice President, Strong Internet
[email-masked] | +1-703-483-9504
internetsociety.org | @internetsociety
pgp: https://josephhall.org/gpg-key
3CA28D7B9F6DDBD34B1016075F86698740A9A871
________________________________
From: Pearg <[email-masked]> on behalf of Christopher Wood <[email-masked]>
Sent: Friday, June 5, 2020 7:34:08 PM
To: [email-masked] <[email-masked]>
Subject: Re: [Pearg] Research Group Last Call for "A Survey of Worldwide Censorship Techniques"

Best,

---

From: Joseph Lorenzo Hall <[email-masked]>
Date: Mon, 29 Jun 2020 22:15:43 +0000

Wow, thank you so much, Amelia!
________________________________
From: Amelia Andersdotter <[email-masked]>
Sent: Monday, June 29, 2020 17:22
To: Joseph Lorenzo Hall <[email-masked]>; Christopher Wood <[email-masked]>; [email-masked] <[email-masked]>
Subject: Re: [Pearg] Research Group Last Call for "A Survey of Worldwide Censorship Techniques"

Dear all,

Without trying to definitely capture all the comments that were made in
the last-call, I have added a bunch of issues on the github with
proposed resolutions to some of the questions raised by you all:
https://github.com/IRTF-PEARG/rfc-censorship-tech/issues

I realized that there are a few things that may, at least from my side,
require further reflection. I'll send a separate e-mail about this.

best regards,

Amelia

On 2020-06-06 01:36, Joseph Lorenzo Hall wrote:
> ------------------------------------------------------------------------
> *From:* Pearg <[email-masked]> on behalf of Christopher Wood
> <[email-masked]>
> *Sent:* Friday, June 5, 2020 7:34:08 PM
> *To:* [email-masked] <[email-masked]>
> *Subject:* Re: [Pearg] Research Group Last Call for "A Survey of
> Worldwide Censorship Techniques"
>
> Based on the feedback and reviews received thus far, the chairs think
> this document needs more work before moving ahead. We will follow up
> with Joe and the other authors to address all feedback in the coming
> weeks.
>
> Best,

--
Amelia Andersdotter

amelia.andersdotter.cc

---

From: Chelsea Komlo <[email-masked]>
Date: Mon, 29 Jun 2020 20:35:04 -0600

Hi Amelia,

On Mon, Jun 29, 2020 at 3:37 PM Amelia Andersdotter <[email-masked]>
wrote:

> On 2020-06-02 16:30, Chelsea Komlo wrote:
> >
> > censor, they are often in a class of their own. I encourage including
> > a discussion of something like "censor maturity" or the technical
> > resources required to implement different techniques. There is a bit
> > of this discussion, but it can be better standardized and applied to
> > each technique. For example, IP blacklisting is trivial and does not
> > require significant infrastructure (and many censors do this), but
> > performing active probing to fingerprint protocols and block them on
> > the fly requires much more infrastructure and planning (and is
> > essentially only China, as I understand).
> >
> I'm hesitant about creating metrics that are specifically designed to
> capture the behaviour of certain jurisdictions. In Sweden, it used to be
> that the internet filtering industry was very strong and innovative. The
> royal family and the Swedish EU Commissioner[2] were heavily involved in
> advancing internet filters around the world. Now the Swedish local
> actors are over-taken by US competitors on both the domestic and
> European markets, for most part, but that's a question of scale and
> resources more than anything else. Also I suppose once the ground-work
> is there, it's easier to build on it - the cost goes down with time.
>
> But it made me think of something else too. Last year, I came across the
> case where a South-East Asian country had bought Chinese infrastructure,
> with government ministers in that country later telling the media that
> they would be able to log into everyone's Facebook account and remove
> posts without Facebook's active involvement or the involvement of the
> user. I sincerely doubted at that time (and still doubt) that the
> infrastructure deployed by this country could actually do that. Probably
> the government ministers had misunderstood the technologies they
> purchased, or wanted to over-sell its capacities with respect to the
> population to make them more afraid than they needed to be of
> repercussions.
>
>
Thanks for the response. My suggestion might have been unclear, so I'll
clarify. I don't think the document needs to give an overview of specific
regions as they are today. However, I do think classifying censorship
techniques by "how much effort it takes to implement" and "how much
technical maturity is required of the censor" helps identify the most
effective techniques to address, as opposed to techniques which are
theoretically possible but not often deployed in reality.

I'll give a heuristic example. Today, blocking based on IP address/domain
is so easy and effective for a censor that more advanced  techniques such
as traffic fingerprinting are not necessary for governments to successfully
censor content. What I have heard from practitioners is that there is
little evidence that fingerprinting-based censorship is being used today at
scale.

As far as this document goes, it will be valuable to provide deeper
classification of censorship techniques based on the cost/maturity for a
censor to implement, to ensure that protocol designers don't target
theoretically possible techniques while overlooking commonly deployed
techniques in practice.

Hope that addressed the above point.
Chelsea

-- 
Chelsea H. Komlo | chelseakomlo.com