I won't vote for a decryption routine in javaScript, would be too CPU intensive and to exposed as algorithm; what about doing this job with an applet and then use javascript to write the content in the document.

Also the applet may cache and prefetch data and so on. You may call it from javascript, have it call javascript or even let it manipulate the DOM direclty.

Also for not "providing evidence of subverting authority" it would be interesting to create a way of wrapping binary objects as ASCII (bad as byte size) that would have a character freq. similar to english.