Assembly Language for Beginners

8.6. “QR9”: RUBIK’S CUBE INSPIRED AMATEUR CRYPTO-ALGORITHM

f=fopen(fin, "rb");

if (f==NULL)

{

printf ("Cannot open input file!\n");

return;

};

fseek (f, 0, SEEK_END);

flen=ftell (f);

fseek (f, 0, SEEK_SET);

flen_aligned=(flen&0xFFFFFFC0)+0x40;

buf=(BYTE*)malloc (flen_aligned);

memset (buf, 0, flen_aligned);

fread (buf, flen, 1, f);

fclose (f);

crypt (buf, flen_aligned, pw);

f=fopen(fout, "wb");

fwrite ("QR9", 3, 1, f);

fwrite (&flen, 4, 1, f);

fwrite (buf, flen_aligned, 1, f);

fclose (f);

free (buf);

};

void decrypt_file(char fin, char fout, char pw)
{
FILE f;
int real_flen, flen;
BYTE *buf;

f=fopen(fin, "rb");

if (f==NULL)

{

printf ("Cannot open input file!\n");

return;

};

fseek (f, 0, SEEK_END);

flen=ftell (f);

fseek (f, 0, SEEK_SET);

buf=(BYTE*)malloc (flen);

fread (buf, flen, 1, f);

fclose (f);

if (memcmp (buf, "QR9", 3)!=0)

{

printf ("File is not encrypted!\n");

return;

};

memcpy (&real_flen, buf+3, 4);

decrypt (buf+(3+4), flen-(3+4), pw);

f=fopen(fout, "wb");