What tools can I use to do this?
— Edit —
I still want to run the code on my site, I just want to make sure no one else can decrypt the code.
The “best” you can do is probably to minify it, which will make it harder to understand it — and a bit of obfuscation might do too — even if someone really motivated will still be able to read it.
See for instance the YUI Compressor, which can both minify and obfuscate JS code.