Prevent running js code after download from site [closed]

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How can I prevent the user running my web page after downlading the page source? We can't prevent downloading the source code, but can encrypt it. But it doesn't good enough for me, because the encrypted code can work after downloading.

Thank in advance.

Answer 1

As a general rule, if the code runs on a remote machine it can be manipulated so they can execute it anyway.

You can make this more difficult through code obfuscation or by implementing some sort of DRM, but I would suggest that this will largely be more trouble than it's worth (since it just takes one person to break it and your code is back out).

1) You could, for example, require that some key be downloaded from a site you control before it'll execute, but the recipient might simply sniff their traffic and pass that value to the game themselves.

2) Or you could possibly set up your game to stream each of the levels or some important aspect of it to your game client, but again, there's not a whole lot stopping someone from just reading these aspects and implementing this mechanism themselves.

3) Perhaps you could encrypt these level packages dynamically on the server with a time-based key, but it just takes that one bored programmer with the technical know-how to reverse-engineer what your method is.

4) Another option that comes to mind is requiring some regular polling to a server you control and requiring some sort of response, but again, if your client can predict what this response is supposed to look like, it's easy for someone to rewrite the game to talk to their own program instead of your server.

5) You could also daisy chain a ridiculous number of dependencies of your javascript logic (breaking your own code into a number of dependencies) so it's slightly more difficult for another user to rebuild the required paths on their system. This might be useful to put off a casual user, but I doubt it'd put off a more knowledgeable user.

All in all, I'd suggest that you simply make the game available as is. Various game companies larger than you have attempted to implement DRM measures of their own with disastrous results (when they don't work as advertised) or just plain annoying for the end user.