MozillaCTF 2012 – Spark: Message in a Bottle (200)

Challenge:

A strangely formatted message has been given to us in a bottle. We know the person who sent the message likes to use cutting edge 3d debugging tools.

When we follow the bottle link, we end up on a page with a lot of 1′s on it. Nicely formatted in a 5×5 pattern. When we look at the source, we see a bunch of javascript:

<script type="text/javascript">
<!--
var s="=iunm? [ ... massive amounts of text cut away for this writeup ... ] =0iunm?";
m=""; for (i=0; i<s.length; i++) m+=String.fromCharCode(s.charCodeAt(i)-1); document.write(m);
//-->
</script>
<noscript>
You must enable JavaScript to see this text.
</noscript>

{Read More}