Using XOR on an Example - Security

Let's XOR our example text file with the password "longpassword123."

%'pl$=#-m:f49ne%!+#*"<#8(=w%#)#<8<s#>+pbml<(nz#8nf"'!zm@DF +u)!!s)?nP$(*-l+p8anw)>:/l9+p8cnp(+=g*>*ebm1y{5{uw

Check out the full C program:

#include <fstream>

#include <stdio.h>

#include <string.h>

using namespace std;

char srcfile[30], dstfile[30], key[255];

void main()

{

   printf("Source file: "); scanf("%s",srcfile);

   printf("nDestination file: "); scanf("%s",dstfile);

   printf("nPassword (up to 255 chars): ");

   //the start of the key preparation process

   for (int i=0; i<255; i++)

        key[i]='§';

   scanf("%s",key); int temp=0; char key_backup[255];

   for (i=0;i<255;i++)

   {

        if (key[i]=='')

           break;

        temp=i;

   }

   strcpy(key_backup, key);

   for (i=temp; i>=0; i--)

       key[temp-i]=key[temp-i] & (~key_backup[i]);

   //key preparation process is done; we're ready to XOR!

   ifstream s(srcfile, ios::binary);

   ofstream d(dstfile, ios::binary);

   if (!s || !d)

       printf("nERROR: Couldn't open one of the files!");

   i=0; char c;

   while ((s.read((char*)&c, sizeof(c))))

   {

       if (key[i]=='')

          i=0;

       c=key[i] ^ c;

       d.write((char*)&c, sizeof(c));

       i++;

   }

   s.close();  d.close();

   printf("nAll done. ");

}

Once again, the download button below leads to an archive that contains the ready-to-run executable and source code of the above algorithm. Enjoy!