[NetBehaviour] Behind the Magic of Anti-Censorship Software.

[marc]

Behind the Magic of Anti-Censorship Software.

Regular Slashdot contributor Bennett Haselton writes in to say...

"The December 1st release of Psiphon has sparked renewed interest in the 
various software programs that can help circumvent Internet censorship 
in China, Iran, and other censored countries. (Some of this interest 
undoubtedly being motivated by the fact that many of these programs also 
work for getting around blocking software at work or school.) Have you 
ever wanted to understand the science behind these programs, the way 
that mathematicians and codebreakers understand the magic behind PGP? If 
you loved the mental workout of reading "Applied Cryptography", have you 
ever wanted a tutorial to do the same for Psiphon and Tor and other 
anti-censorship programs?"

Well, here's a primer, but you might be disappointed. Like making the 
Statue of Liberty disappear, it doesn't sound very cool once you know 
how it's done; the truth is that most anti-censorship programs, 
including mine, only work because the censors are not trying very hard.

(Note that I am going to be talking about ways that certain 
anti-censorship programs can be defeated. I don't believe that this is 
giving much help to censors, because these are obvious weaknesses that 
would occur to anyone who knows how the programs work. For reasons I'll 
get into at the end, I don't think these weaknesses actually make much 
difference.)

Basically, all anti-censorship programs fall into two categories: those 
that require you to have a helper outside of the censored country, and 
those that don't.

Take Psiphon. To use Psiphon, someone in a non-censored country has to 
install it on their home computer, which turns their computer into a Web 
server with an interface similar to Anonymouse.org, where you type in 
the URL of the page you want to view and it fetches it for you. The 
difference, of course, is that Anonymouse.org is widely known and 
blocked by any self-respecting Internet filtering system, while your 
newly created Psiphon URL pointing to your home computer is not blocked 
anywhere, yet. So if you set up a Psiphon URL on your computer in the 
U.S. and e-mail it to your friend in China, your friend can use it to 
surf wherever they want. (Note that this also has the desirable property 
that the person in China doesn't have to install any software, so they 
can use the URL even from a cybercafe computer with restricted user 
permissions.) The hurdle, of course, is that the person in China has to 
have a contact outside the country to help them. This is not a huge 
barrier for many Chinese, but it still means the program doesn't have 
the instant gratification property of something that you turn on and it 
just works.

more...
http://yro.slashdot.org/article.pl?sid=06/12/20/1336245