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smilleme

protection my program

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Hi,

The article is nice and informing,
but if you want to do it on pc you might need
to take some things into consideration.

Firstly, modifying code is not going to be failsafe on pc,
because reading and writing of code in memory may trigger windows protection
or the recently implemented CPU buffer overun protection flag.

Secondly, you might need simpler protection mechanisms.
Firstly, do not under any circumstance, use strings in the dialogs or the drawing code that shows the user "you have a hacked code". This is the first thing a cracker would look for. Adding the XOR technique explained in the article and some perverse code obfuscation may sigificantly delay the cracker. Also you need to detect when the code is being debugged and insert something similar to their checksum modification at breakpoints insertion. You may here check for the processor's special setup done when debugging, or use runtime checksums on the memory code (which would be modified to include the breakpoints, thus altering the checksum).

But as they say, it is impossible to stop a cracker, so you need to know what sort of target audience your game has. If it is low profile, you may do with simple verification techniques. Perhaps add some online authorisation. These work well when upon authorisation the game receives a key that is in a way integrated in the code itself (a part of it is executable code, designed, for example, to use certain instructions only avaiable on the target machine (sse2/etc), or check the serial number of the hard drive).

Use threads and multiple checking points with different methods of doing the checksum if you need to slow down the cracker more. (same checking code can be searched easyly, unless obfuscated, or mutated, in polyform virus terminology). And, best of all, employ the delayed "you've been detected" technique explained in the article.

Best of all, try some disassamblers and some cracking tutorials on the net to have first hand experience on what a cracker does. (be aware though that cracking is illegal, even if you have bought the software you crack, so do not leave under no circumstances the cracked versions "leak" to anybody else.)

That's my 2 centz.

Tudor

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