Protecting EXE/DLL's

I need to protect my DLL and EXE files from being modified (patched).
In the past I have used PKLITE. The compression included a CHECKSUM and
the program was verified at startup. However PKLITE is not available for
Win32 EXE/DLL's. Any suggestions would be helpful.

[Vasko]

Whatever you do, you can not be sure that your EXE/DLL files will not be patched. The exe compression utilites indeed compress the and keep the checksum, but there are uncomperss utilites doing the opposite to those :)

If it is a matter of anti-hacking techniques better give up. It is best that you do not waste afforts in this case. For example look how many hard-protected software is broken on hacker sites. All modifications in YOUR program is a matter of time for these guys.

To protect your exes from accidential corruping and ensure your program's algorythm is OK you may test your program's main functions by calling them at startup with sample input, expecting correct output. For example encryption systems do this at startup to ensure the data they are going to encrypt will be decrypted correct (i.e. the algorythm works OK).

[Jason Coene]

If you are talking about anti-cracking routines, your in a tough situation. If you just want it so a virus cannot infect a paying customer's system, simply create an individual application, which starts when windows does. call it protect.exe, and put protect.exe and app.exe in the same directory.

protect.exe, can simply call:
FILE *f;
f = fopen("app.exe", "wd");
//hang here

now, the app is protected so nobody nor any application (system) can read or write to the file.
Hope this is what you were looking for...