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cozzie

How to 'ship' your game assets

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Hi,
Like many of us I'm working on the next top gaming title. But before that, just doing some small games.
When I finished my first game I ran into something quite basic but never thought off.

My game folder concists of:
- an executable
- a data folder with sub folders for textures and sounds (bmp, png, tga, wav, mp3, ogg)
- some ascii files with highscores and own file format 3d scene information
- some X files (binary) with 3d meshes

What I want to prevent is to have all these assets and files 'open to public' within a grasp.
How would/ do you do this?

A few first thoughts:
- compress them all to a ZIP file, rename extension to i.e .abc
at runtime unpack the contents to a temporary folder (with some ZIP/ compression API).
Remove the files when application quits (how to handle non sunny quitting?)
- use some sort of DIY encryption and rename the file extensions
- ....

It's no problem if it's not waterproof though.
Really like to know your ideas and suggestions on this.

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You could always make your own format, the header would be an index (which associates file 'paths' with file offsets). Each file could be individually compressed, maybe even based on its data type, as audio and images are more efficiently compressed using methods suited to each. Perhaps even a layer of encryption, on the index header, and each asset itself, using your basic XOR against some generated value (from the asset's offset, name, etc)..

 

It's not difficult to write up a quick utility that will search out all the files in a folder, and its subfolders, and add them to such an asset package.

 

The *last* thing you want to do is extract an asset back to the disk, just to load it from there. You need to re-write your code so that it directly loads the asset from the packaged file. Writing it out to disk to load it is just silly.

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Guest Hiwas

You are about to waste your time.  Once the game is in the hands of the user, you can encrypt, obfuscate and do anything else you want and it still takes about 10 minutes for anyone to browse textures, meshes etc.  Between DX intercept programs or format browsers such as http://multiex.xentax.com/, your users can get anything they want quickly.  Especially if you tried to encrypt the data, you have to provide the key so it doesn't take long for someone to dig that out and open the assets directly even if they don't want to use a DX intercept program.

 

You can of course do as you desire, but there is really little reason to put any effort into this just for obfuscation reasons.

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Thanks. Those are 2 completely directions :)
I personally think to agree withoption 2, don't waste all the time. Maybe for the feeling just rename files to associate them with my own code. Regarding the ascii files I might want to think about some sort of easy encryption (to just increase the effort needed to change quite some essential things in the game, like the highscore table :))

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Guest Hiwas

I can understand 'wanting' to secure some data but really, once it is on the players machine, there is nothing you can do they likely can't hack in less time than it takes you to implement it.  A highscore table is just as invalid if they hack collisions/lives/etc as it is if they simply modify it directly.  So, why waste the time?  The only way to secure data is simply not give it to the user and store it on a server, of course garbage data in from hacked clients is still possible and invalidates the server data also, yer pretty much screwed either way..  :)

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One option is to not encrypt your data, but instead to hash its data when you load it to verify that the contents of the file haven't changed. You can precompute hashes of files, store then in your program in some array/map of strings or bytes, and when you load a file take the MD5 or SHA-1 hash of it and verify that it's the same.

 

You can also mix this up with other encryption/obfuscation schemes.

 

Of course, if someone wanted to hack your game, it would literally take them only minutes to figure it out and hack your game (regardless of what you do, encrypting, obfuscating  hashing, etc.), so I wouldn't bother with it. Once one person figures it out, he/she can make a tool for everyone. It's not worth your time, most likely. But of course, if you're programming for fun, and you have fun encrypting/obfuscating/hashing/etc, then go ahead and have some fun.

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Personally I store my assets as resources. (the Microsoft specific standard that stores icons, menus, some strings, bitmaps etc or custom data if you want)

I assume with resource editors it's still as simple to extract non-encrypted files of course but I can ship a stand-alone exe that self-contains everything.

If this solution interests you, look into the following functions on MSN: FindResource(), LoadResource(), LockResource()

The custom type is RT_RCDATA and is "defined" as 10. You would need to pass that value to the FindResource() function.

 

As an aside, I disagree that encrypting/obfuscating a program is useless because somebody in the world (a clever hacker) will undo that anyway. You can still buy some time and avoid every script-kiddie and his grandma to already steal your assets. If it were really useless then AAA titles wouldn't go to so much trouble doing it. Whenever you ask how to do this here, you are either suspected of wanting to bypass such a scheme yourself to steal a game (which sort of proves that such a system IS useful or why would they be so afraid that you bypass it) or maybe there is some elitism in which newbies aren't encouraged to be able to code to the same protected standards.

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There are some older threads with a similar subject here on GDev, and some of the posts in them make a great point on the subject - in fact, it would be a shame not to reference them:

http://www.gamedev.net/topic/506247-why-do-game-companies-use-custom-texture-formats-instead-of-the-dds-format/

http://www.gamedev.net/topic/605910-encrypting-images-png-with-directx/
http://www.gamedev.net/topic/577588-what-are-some-simple-ways-to-protect-my-games-assets-sprites-sound-music-etc/
http://www.gamedev.net/topic/316093-protecting-game-assets/
http://www.gamedev.net/topic/627723-packing-the-game-resources/
http://www.gamedev.net/topic/547471-protecting-shader-code/
http://www.gamedev.net/topic/555394-binary-file-writing-making-it-unreadable-c/

To my view, the point most people make against the encryption-for-protection idea is that the best kind of protection for your assets is the legal one. Make a good copyright claim, a good EULA document.
But they do make a point for managing your game asset file formats in a sense that you should write it in a game-engine specific, binary manner so as to load it as fast as possible (meaning just dumping the data to memory and setting up your pointers, without having to parse data extensively). This kind of binary file formatting provides a "side-effect", unintentional protection as you wouldn't be dealing the original formats anymore. So as Hannah Montana would say, it's the best of both worlds.

Edited by Kryzon

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Guest Hiwas

As an aside, I disagree that encrypting/obfuscating a program is useless because somebody in the world (a clever hacker) will undo that anyway. You can still buy some time and avoid every script-kiddie and his grandma to already steal your assets. If it were really useless then AAA titles wouldn't go to so much trouble doing it. Whenever you ask how to do this here, you are either suspected of wanting to bypass such a scheme yourself to steal a game (which sort of proves that such a system IS useful or why would they be so afraid that you bypass it) or maybe there is some elitism in which newbies aren't encouraged to be able to code to the same protected standards.

I have never encrypted data in a game client and I've shipped quite a few.  Not bothering has nothing to do with elitism, or any particular belief things should be open/free for access, it is simple practical reality, it doesn't work and is a waste of time.  Additionally, if grandma wants to make her character pink instead of brown, more power to her as long as she enjoys the game and hopefully paid for it.  The only typical encryption in AAA titles, and it's just obfuscation really, is because the formats are written custom with practical reasons in mind such as speed, i.e. pack files are used by many games purely because it is hugely faster to load multiple pieces of data from a single already opened file than it is to load from multiple loose files.  Often the data is also compressed, again, this is not usually an attempt to increase obfuscation or implied encryption, it is just a practical reason that at the cost of some CPU it is faster to load and decompress than wait for an HD to read in the entire uncompressed piece of data.  Or the data looks like garbage but is really precompiled script VM or other things like that.

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Perhaps something like BoxedApp is what you're looking after? It packs files into the executable and unpacks them in a virtualized environment for your game.exe to use. I'm not security expert at all (really, I haven't got the slightest idea what I am talking about!), but as far as I am concerned it gives you basic protection against DLL-injections and hides your resources from public view. Also you get a single binary for shipping. No installation required, just click the exe and run the game. Registry-values is saved in a virtual registry.

Edited by Kuxe

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