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floatingwoods

copy protection between 2 dlls

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Hi, I have two dlls that I want to copy-protect. I know there are many different ways of protecting an exe file, but nothing is "uncrackable". However, when using a dll that for instance contains calculation routines, there might be a more specific and efficient method? Additionally, the dll will be used always in conjunction with another dll. Is there a way that each dll checks on the other mutually in some way and so make the cracking more difficult? I was thinking protecting each dll with a hardware-ID specific serial number in a file, then also checking each dll's checksum mutually (dll1 checks the CRC of dll2 and vice-versa). Is that a good approach?

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Using DLLs makes breaking protection even simpler. Crackers can also provide their own version of DLL which has no protection. Very convenient, better than patching an exe.

If someone is capable of breaking protection at assembly level, the file extension will make no difference to them.

Also, unless you're proficient in cracking such protection yourself, you have absolutely no chance of securing your code. It's akin to security company trying to install burglar protection, but never ever looking at what burglars do, nor the tools they use, nor how they operate. They will think that putting a sign on front door saying "Does not open" is a great idea.

For example, most home-made schemes add something like: "if (!isProtectionValid()) Exit()", which requires a simple search and replace of a single bit, thereby bypassing entire protection scheme, no matter how elaborate.

You have three possibilities:
- License one of existing third-party copy protection schemes
- Make application online
- Make your application such that nobody will want to use it

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theres some underground technical stuff explaining how they broke the WMV drm. the document has some explanation of how the files are protected. It was published to a darknet under pseudonym Beale Screamer - you can google tons of mirrors. Here's one.

Here's a philosophical bit at the end for good measure:

Quote:
However, it's easy to see where software bloat and inefficiency comes from when this code is examined: every main DLL has a separate copy of the elliptic curve and other basic crypto routines, and parameters passed back and forth between modules are encrypted giving unnecessary overhead, not to mention all the checks of the code integrity, checks for a debugger running, code encryption and decryption. Perhaps you felt this was necessary for the "security through obscurity" aspect, but I've got to tell you that this really doesn't make a bit of difference. Make lean and mean code, because the obscurity doesn't work as well as you think it does.

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