On 2012-10-09, Jon Elson wrote:
DoN. Nichols wrote:
Assuming that all three numbers could be any of the 100, that
leaves 1,000,000 combinations to try. Normally, you are advised to
avoid number near zero (especially on the last one, but assuming that
you avoid 98 through 02, that still leaves 857,375 combinations to try.
(And also consecutive numbers should not be too close to each other,
which reduces the count a bit more, but not really enough. :-)
Well, Richard Feynman was able to crack the safes at Los Alamos
in a couple hours, and I assume they were of similar specifications.
Not clear what tricks he used.
Among other things -- he knew the mindset of the individual
people who set the combinations, so the number of tries was
significantly reduced.
Things like a physicist being likely to use physical constants
as combinations, mathemeticians likely to use "pi" and "e" as
combinations, auto license plate numbers, dates of birth or marriage,
names of spouses, kids, and pets and similar -- and they were not
required to change them as often as later.
I know that we had to change them about every six months, and
were in the habit of using words -- converted todigits by the telephone
dial (ignoring 'Q' and 'Z'). There was always a phone near the safes,
so this was a convenient way to do it.
Once, decades ago now, a sequence of three security file
cabinets in one room was set to "howcum nobody toldme" or 46-92-86-(0),
66-26-39-(0), and 83-63-63-(0). This was making fun of a common phrase
of one particular co-worker. :-)
Some of these have all sorts of suicide devices in them, such as
tempered glass plates that shatter when you drill in the wrong place,
and totally jam the works. You then have to saw the entire door in
half to get it open.
Since we had nothing above "Secret", certainly not "Top Secret"
or any of the crypto or nuclear secrets (at least in our area) and most
was just "Confidential" or "FOUO" (For Official Use Only), we did not
have anything this Draconian.
The closest to this is a couple of data encryption devices which
I got at a hamfest (with the Medco keys for the locks), which was set up
so you needed both keys to get to the bolts which kept in in the rather
thick metal housing (one key for normal use, and the other for loading
new encryption keys into it), and you had to spend a long time taking
out a long fine-threaded screw. The first thing that happens as you
start to back that screw out is a metal arm is lowered to short out the
power to the CMOS RAM chip which kept the keys, so even if you got
into it, you could not read the keys (and they would normally be changed
in a week anyway. :-)
BTW -- for setting the encryption keys on a Wi-Fi device, I will type a
fairly long paragraph, and then take a MD5 checksum of the
paragraph and use *that* as the key. It is a good match for the
maximum length of key the devices will accept. As an example,
let me take *this* paragraph up to the colon:
And it comes out with "eab0d091f3856c6253db169628dac12f" as the
key.
And for an example of how little a change makes how big a
change, my editor in the test above always adds a newline to the
end of the last line so I went into it to take off that with a
different editor, and got "fa9482e83bfad920695d9022a561cc2a"
And convert it to a MS-DOS format (CR & LF at the end of each
line) and it becomes: "76c2b9fccab610d5afa16ba685918b30".
Unix uses only a LF (line-feed) (which it calls a "newline"
character at the end of each line, and older MacOS (pre OS-X
which is really unix with a fancy GUI over it) used only a CR
(Carriage Return) at the end of each line.
However, the changes don't matter, since you generate it *once*,
and then type it into each system that needs it.
Enjoy,
DoN.
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