One minor irritation on my recent trip to China was
discovering that Facebook and Google+, where I normally waste time arguing with
people, were both blocked, as was blogspot and hence my own blog—the reason this
post is only going up now, from Hong Kong. I gather that locals have ways of evading
the restrictions but do not know the details. Which lets me try to figure out how I would do it.
The obvious solution is a proxy server. You connect to it
from inside China, it connects you to any other site you like, blocked or not.
The obvious problem is that whoever is doing the blocking notices and blocks
the proxy server. To which one less obvious and so more interesting solution is
Start with ten thousand proxy servers—or at least ten
thousand URL’s, possibly all connected to the same hardware. You
email each of your customers a URL to use.
Unfortunately, some of your customers are
spies, employees of whatever state organization does the blocking. They report
the URL’s they get to their employer, who blocks them.
At which point you observe which URL's are blocked and note
which of your customers got those URL's, hence which of your customers you suspect
of being spies. Since customers who got the blocked URL’s now
cannot access your server, you send them new URL’s—a different new URL for each
of them. You observe which of those get blocked. You now have a pretty good guess which of your
customers are spies.
So you have one set of URL’s for the spies, another for
everyone else. Whenever a URL gets blocked, you send the customers who had that
one a new URL—and add those customers to your list of possible spies. You
continue with a policy of sending real customers URL’s that don’t go to
confirmed spies and updating your list of confirmed spies on the basis of
which URL’s get blocked.
So far as I can tell it should work. I have no idea whether
or not I have just reinvented something close to what already exists.