Thread: BYTES(More Info)

Ok,
I will try and improve my query. I am trying to do an exhaustive search to find a key. That key is 32bits, but I have reduced this search by finding out which key bits are effective (ie: effecting the output).

I have therefore eliminated the final byte and bit 7 from this exhaustive search, leaving me with 23 bits of possibilites for the remaining bits. 2^23 is much less than 2^32.

I now need some way to cycle through the possibilities for the remaining 23 bits. At the moment I have split it into 4 bytes and set the last byte to 1 (it can be anything:it doesnt matter) and the same with bit 7.

Now, here's an example:
from left to right: bit0 -> bit31

key={XXXXXXXX 00000000 00000000 X0000000}

"bits set to X is a don't care"

I need a way to get all possible values for the above key.

eg: key={XXXXXXXX 00000000 00000000 X0000000}
key={XXXXXXXX 00000000 00000000 X0000001}
key={XXXXXXXX 00000000 00000000 X0000010}
key={XXXXXXXX 00000000 00000000 X0000101}

all the way to
key={XXXXXXXX 11111111 11111111 X1111111}

now if i try and go around a loop 2^32 and get all possible values I will never break out of it......
thats why I have reduced the number of bits to 23....

any ideas please

> key={XXXXXXXX 00000000 00000000 X0000000}

Code:

long int x, y, key;
for ( x = 0 ; x <= 0x00ffff00 ; x += 0x100 ) {
  for ( y = 0 ; y <= 0x7f ; y++ ) {
    key = x | y;
  }
}