Thread: BYTES(More Info)

  1. #1

    BYTES(More Info)

    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

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    > key={XXXXXXXX 00000000 00000000 X0000000}
    long int x, y, key;
    for ( x = 0 ; x <= 0x00ffff00 ; x += 0x100 ) {
      for ( y = 0 ; y <= 0x7f ; y++ ) {
        key = x | y;

  3. #3
    ATH0 quzah's Avatar
    Join Date
    Oct 2001
    Hey, Salem, long time no see.

    Hope is the first step on the road to disappointment.

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