[casual_games] Encrypting text files

[John Foster]

Ricky,
I use a variety of methods depending on how much security my application
requires.
 
- MD5/crc - calculate a crc on the file with a secret key and save the hash
in the file. if the file is altered the hash won't agree with what you
recalculate. This method is fast and simple and leaves the data file in
text, which can be a benefit for debugging and troubleshooting.
 
- blowfish encrypt the entire file. relatively fast and simple but the file
won't be readable. could be a support issue.
 
- zlib the file but enhance zlib with either the crc or encrypting the
result. this is the most complex and least efficient but it's much more
secure. if you have something to protect then the people you want to keep
out will find a way in, so zlib alone isn't enough.
 
keep your keys safe.
--John
 
 

  _____  

From: casual_games-bounces at igda.org [mailto:casual_games-bounces at igda.org]
On Behalf Of Ricky Haggett
Sent: Tuesday, January 15, 2008 1:38 PM
To: 'IGDA Casual Games SIG Mailing List'
Subject: Re: [casual_games] Encrypting text files



Ø   The ZLib API is very simple to use. We integrated into our file system
abstraction layer so that any file can be transparently (to the game code)
compressed on load and/or save.  

 

Marvellous news – these are two properties I was hoping for in any solution.
Thanks James.

 

 

Ø  where's the harm in someone mucking around with their play experience?

 

If the game in question was non-commercial, and would suit some
circuit-bending modification, I’d say no harm at all – in fact I’d encourage
and aim to support some mucking about.

 

But if it’s try-before-you-buy, the ability to edit the save game to unlock
everything and experience all the content right away represents a failure
case in my book.

 

 

Ø  You can save binary files instead of plain text

 

There are plenty of advantages to plain text though Miguel – it’s great to
be able to edit and reload text quickly without any obvious
conversion/packing process, and the ability to open save game files as text
and sanity-check them can be really handy. A Gui is also a pretty good fit
for xml – we don’t have an in-game editor that can do this for us yet - just
trusty Notepad++. I was only dimly aware of the ability to compile lua into
bytecode, so thanks to the folks who pointed this out.

 

Ricky

 

 

 

 


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