Well, we are going to talk about internet censorship.
So the main components of a communication are usually
Who is talking to whom, and what are they talking about?
So usually the who portion is called the user,
The Whom portion is called the publisher,
Which provides some information to the user.
and, the what part,
Is the information Itself.
So... internet censorship,
Comprises of...
A range of steps that the censor might take
to either stop the publication of information, on the publisher's side.
Or discourage the access to that information or the link that connects the user to the publisher.
Or directly coerce users to not access that information.
But the key point is to stop the information from being disseminated.
I'll give you a very simple example of how censorship takes place,
Which would kind of gives us also an Idea
Of what are the different mechanisms available.
If youtube.com has been blocked,
and I am a user
Usually the set of steps that would take place is that I would type "youtube.com" into my browser,
Then behind the scenes my browser would generate a query to a DNS server.
okay it was "youtube.com" but now it's "abc.com"
so it will generate a DNS Query to the local DNS Server asking
"what is the IP address to which I should map abc.com?"
now, either the DNS server would already know the IP address corresponding to abc.com
Or it would ask other DNS servers, recursively, on the internet,
and somehow find the IP address corresponding to abc.com
Once it has that IP address it will return that IP Address
to the user
Then the user's browser will use that IP adress
to connect to abc.com
which is at 1.2.3.4
and send an HTTP Get Request
for some index page.
and if it all works well,
then abc.com will respond with the corresponding webpage
now as you can see this involves interaction between different entities.
What a censor can do,
is that it can block the user's connection at this point
so when the user asks for the IP adress corresponding to abc.com
the censor controlled DNS server could either say that this domain does not exist.
or it can say that oh,
the IP address corresponding to this domain name is 4.4.4.4
which is something which is under the control of the censor
this is called DNS Redirection or DNS Sinkholing
then, at the IP layer,
Say, if it doesn't block the connection at this layer,
then in the next step
what a censor can potentially do is that it can block,
user's attempt to connect to 1.2.3.4
which is called IP Blocking
and then there's this concept of application layer blocking
which dosen't involve the domain name, or the IP Address
but rather a sophisticated censor might be able to look at the content,
that is traveling over this channel between the user, and abc.com
and if it finds some offensive keywords
which are indicative that this connection is
carrying some information which should be censored
then based on that keyword
it will send TCP.. it can potentially send TCP
reset packets to both sides
or do something else to just,
drop packets to just disrupt the communication
[offscreen] Break the Connection, OKay
do people get into trouble when they try in to get in these sites? What's it?
is that something that can be traced, when if...
yes
yeah. So...
when we talk about the human element of censorship resistance
this involves publishers of information and also the users of information
and...
that basically goes into the area of privacy.
and anonymity
so basically anonymity ensures
that the users of a censorship resistance system
may not be traceable.
and...
what you just mentioned is called coercion of users or coercion of publishers
and ideally one of the goals of a comprehensive censorship resistance systems
is to afford that kind of privacy to users
but usually they don't do that and that's usually something
that users have to take care of themselves by
by combining their use of censorship resistance systems with anonymity services like TOR
[Off screen] I know that a long time ago people would block out things
in newspapers or blockout things in images and that would be a form of censorship.
So how does it work then when people are censoring in these levels we've just talked about
and yet there's censorship resistance software out there, what's going on, what will be the next "thing"?
I think it's like an arms race, right? because the technology
that is used to disseminate and retrieve information is constantly evolving
so now we have social media websites like Twitter,
Facebook, which have loads and loads of users generated content
so on the one end it's very difficult for a censor
to retain that control of information
because now there is this whole bulk of information
to go through
and then also because this content is hosted by sites like
Google or Twitter
so they can't just block the IP address of Twitter
and block the IP address of Google
because that would incur alot of collateral damage
the false positives that we previously talked about.
but when the censor ups their game
then the censorship resistance systems also take the next step up
so there's basically a cat and mouse game which is in play here.