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.
If you truly want to encrypt it so that no one else can decrypt it, you could use one of any number of encryptions. For instance, to do it manually, you could use TrueCrypt; or to do it programatically, use the encryption libraries available in most languages.
There is no way to do that. You can obscure it and have some domain checking code in it. Or you could have it served with a server-side script that checks the referring domain.
I think you're confusing encryption with compiled binary.
Not even commercial closed-source software such as Microsoft Office or Adobe Photoshop are encrypted for distribution. But they are compiled to native machine code, which makes them hard to reverse engineer.
.pyc files, maybe we'll have a
No such thing exists yet though. And even if it did, this is just a more intense obfuscation. Obfuscation is fine for preventing casual copying and sharing, but if you need really protect your intellectual property, move the logic server-side.
There is no way to do so because at the end of the day, the code still has to run, unencrypted, on the client machine, which means the routine to decrypt the code has to be sent alongside the encrypted code. You're handing them both the lock and the key, all they have to do is turn.
Your best best is to run it through an obfuscator, but even then, its not like somebody won't be able to just rewrite it themselves without the need to attempt to read your code anyway.
What you want is theoretically and practically impossible. People will tell you here that it is not possible and you might think "Well, that's because nobody has tried hard enough". No. It's impossible in the same way that calculating the nth prime number in linear or constant time is impossible. It's impossible in the same way that the halting problem is impossible to solve. "What do you mean 2+2 doesn't equal five? You're not trying hard enough!"
Not only is it impossible though, but the motivations for wanting this sort of thing are normally pretty misguided. It's always a fundamental mistake to attempt to use technology to solve a problem that is fundamentally a legal problem. You want to protect your code from "pirates" or competitors, perhaps? It's not likely that you've written anything particularly worth stealing, but if you have, and you don't want people to steal it, then your only true recourse is the rule of law.
However, on a larger level, your problem is not likely going to be competitors or pirates stealing your code. Your problem is going to be business oriented: Gaining an audience through making a quality product, and the right price, and with sufficient marketing. You do that right, someone stealing your code doesn't matter. You do it right, and having the "authentic original" will appear to have real value. In fact, if you release your stuff open source, it can only really help you, because then you have an army of interested amateurs working for you for free, potentially. Piracy and reverse engineering is actually a godsend because it means people are interested enough in your product to want to improve it. The best thing is to do whatever you can to let that happen.
If this is not a business effort, then I really have no idea why you're even bothering. Proper credit?
The best minimizer/obfuscator is probably Google Closure Compiler - it's very advanced and might turn your code into something very hardly understandable.
What you're looking for is obfuscation, not encryption. There are tools such as JSMin and the YUI Compressor that will make your code very unreadable, to the point where no one would want to try to make sense of it. However, there is no way to make it so that someone can't copy and paste it onto their own website and run it there. I wouldn't worry about it, honestly, because you'd be wasting your time trying to protect something that can't be protected. Try putting all your "important" logic on the server-side, if possible, because that's the only foolproof way to do it. If the browser can access it, so can anyone else.
This is exactly DRM: you're giving the user a lock, and also the key to it, and expecting to be able to say what they can do with it.
It's theoretically impossible: if their computer can execute the code, it has to be unencrypted there.
It's practically impossible, too: look at everybody watching DVDs on Linux boxes to see how successful you can be.
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