Question

I am writing a C app on Windows with MinGW/gcc. I need to use the #include directive to include a file that contains an encrypted string. The string will be decrypted at runtime. I want to do this so the string will not be visible if looking at the executable with a hex editor.

I tried this, but it doesn’t work. You get the idea, though:

char *hidden_str =
#include "encrypted_text.dat"

There may be unescaped stuff in there that’s confusing the compiler. I don’t know. I don’t know what happens to it after it’s encrypted.

If there’s a better approach to this, I’m open to it.

Answer 1

If you installed and configured MSYS when you installed MinGW, you should have access to a command called xxd, which takes a hex dump of a file. By using the -i command line flag, you can get it to output a C-friendly file which you can easily import.

An example call would be:

xxd -i in_file output.h

The contents of output.h would then look like:

unsigned char in_file[] = {
  0x68, 0x65, 0x6c, 0x6c, 0x6f
};
unsigned int in_file_len = 5;

You can then include that file into your C source code and have access to it:

#include "output.h"

unsigned int i;
for(i = 0; i < in_file_len; i++)
{
    printf("%c", in_file[i]);
}