Thread: adding encryption to bmp

hey ppl...
well here's a chalenge; I made a XOR encryption program but I want to hide my encrypted file inside a bmp...

the program should encrypt the file and then would, at the end of the bmp, add the encrypted file...

I've got only one problem... what can I use to let the program reading the bmp (in binary) know where the encryption starts???
and how can I be sure that other bmp viewers would'nt show that as curropted area in the bmp???

I know it's a bit tricky but would help me a lot if you can give me the code....

thanks in advanced

I forgot to log in!

klausi

I didn't quiet get you there.. is there a code or a tutorial you can show me how to use that???

Here's the idea with a text file, you can do the same thing with audio, video, and static pictures as well though it takes a bit more work:

Code:

#include <stdio.h>
#include <stdlib.h>

static void ensteg ( void );

int main ( void )
{
  ensteg();
  return EXIT_SUCCESS;
}

void ensteg ( void )
{
  FILE *crypt, *mask;
  int c, f, x, y;
  char bRaw[8], bRev[8];
  if ( ( mask = fopen ( "mask.txt", "r" ) ) != NULL &&
       ( crypt = fopen ( "ensteg.txt", "w" ) ) != NULL ) {
    printf ( "Enter a string\n" );
    while ( ( c = getchar() ) != EOF ) {
      for ( x = 7, y = 0; x >= 0; x--, y++ ) {
        while ( ( f = getc ( mask ) ) != (int)' ' )
          if ( f == EOF ) rewind ( mask );
          else (void)putc ( f, crypt );
        /* Break the byte down into bits and
        ** convert each bit into its char
        ** equivalent.
        */
        bRaw[x] = (char)!!( c & ( 1 << (unsigned)x ) ); 
        bRaw[x] = bRaw[x] % 10 + '0'; 
        bRev[y] = bRaw[x];
        /* Place the bit in the text file
        */
        if ( bRev[y] == '1' ) fprintf ( crypt, "%c ", f );
        else (void)putc ( f, crypt );
      }
    }
    /* Finish reading the mask file and close
    */
    while ( ( f = getc ( mask ) ) != EOF ) (void)putc ( f, crypt );
    fclose ( mask ), fclose ( crypt );
  }
  else
    printf ( "ERROR: File open failure\n" );
  printf ( "Press any key to continue" );
  (void)getchar();
}

The nice thing about this program is it's simplicity, each byte in a message is broken down into individual bits and printed as spaces accordingly. One space for binary 0 and two spaces for binary 1; the end result being a file that looks like it was badly formatted.

-Prelude

but.. . I'm still confused about the way... Isn't there any tutorial about this sort of stuff...
Prelude I'm sorry but I can't grasp what your doing here!!!
what do you mean by breaking the byte into bits and why would I use the spaces???

sorry I'm still confused

>what do you mean by breaking the byte into bits and why would I use the spaces???
My example was for text files only, the concept behind the program is that a char has a certain number of bits (8 was assumed in this program), each bit having either the value 0 or 1. The program uses this line
bRaw[x] = (char)!!( c & ( 1 << (unsigned)x ) );

to extract individual bits from an 8 bit char and places it in an array. The program then places each bit into a prewritten text file as a series of spaces in between the words, if the end of the file is reached before all of the bits are encoded as spaces then the file will rewind to the beginning and start over. So if you have the message "Hello", you can break each character into it's individual bits:
H = 01001000
e = 01100101
l = 01101100
l = 01101100
o = 01101111

Place this in a text file that already has something in it and you get a result similar to this:

Code:

Steganography is  the art of  hiding information in plain view  so  as 
to confuse  seekers of  that information.  A  steganographic 
program  is  one that places binary  data  in unlikely  places  
such as the noise  of  an image  or  small  amounts  of static in a sound file.

Take node of the unusual spacing, if you count the spaces where one space is a 0 and two spaces is a 1 and place them in groups of eight, you get this:
01001000 01100101 01101100 01101100 01101111

Which can then be converted to the ASCII equivalent, which is:
Hello

>arent you going to have a text file or whatever 8 times bigger than the original?
Yes, which is why the program rewinds the file if it reaches the end and a much larger mask file hides the message better.

-Prelude