With all the recent hype about JavaScript and HTML5 replacing Flash, I wanted to know – How would it be possible to protect client-side js code? Of course, it is possible to obfuscate it, but that would only make it a little harder. Also, for games which submit high scores to the server, wouldn’t it be incredibly easy to modify those scores before they are sent to the server? I know even Flash files can be decompiled, but they can be obfuscated and flash decompilation is not as easy as modifying data in JS – could be done easily using a plugin such as Firebug. I’d like to know everyone’s views on this.
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Javascript, being parsed on the client, is never 100% safe. There will always be ways to find out what it does. A few days ago I’ve even seen a tool which unpacks packed javascript so the only thing you can really do is using “ugly” variable names (or actually, make a javascript packer transform your “good” variable names into short/ugly/nonsense ones)
To protect game results, you have to move some of the game logic to the server so the client cannot send arbitrary results.
Summarizing it: Don’t put secrets in javascript code and don’t trust anything coming from the client – no matter if it’s from a form or generated/submitted via javascript.