Hey China web surfers!  Remember back in the day when you could use the Google cache to get at web pages that may have been taken down, or to view the HTML versions of PDF files and Microsoft Word documents?  And then, the authorities at the Great Fire Wall decided to block Google's cache service because it was being used to access blocked material?  Well, thanks to a link I found in <a href="http://del.icio.us/imao">Isaac Mao's <abbr title="Delicious Social Bookmarks">del.icio.us</abbr> links</a>, I think I've found a way to get this functionality back.

The very cool Harvard-Toronto-Cambridge <a href="http://www.opennetinitiative.net/">OpenNet Initiative</a> has published <a href="http://www.opennetinitiative.net/bulletins/006/" title="OpenNet Initiative: Google Search & Cache Filtering Behind China's Great Firewall">a bulletin</a> revealing their finding that the Great Fire Wall blocks the Google cache by killing connections that request <em>any</em> URL containing the following string:

<quote>search?q=cache</quote>

Knowing this, and knowing a little bit about the way URLs work, it should be easy to formulate a URL that requests a page from the Google cache without using the aforementioned string.

The way I did this was to replace one of the characters in the string with its hex equivalent preceded by a percent sign.  For example, <q>q</q> has <a href="http://www.newebgroup.com/rod/newillusions/ascii.htm" title="Table of ASCII Values">the hex value of 71</a>, so that <q>q=cache</q> can be replaced by <q>%71=cache</q>.  For example, I take the address of the cached copy of Google's own homepage:

<quote>http://64.233.167.104/search?q=cache:zhool8dxBV4J:www.google.com/+google</quote>

and change it to:

<quote>http://64.233.167.104/search?%71=cache:zhool8dxBV4J:www.google.com/+google</quote>

Readers in China, try it out:  <a href="http://64.233.167.104/search?%71=cache:zhool8dxBV4J:www.google.com/+google">Google cache of the Google homepage</a>.