[7922] in bugtraq
Re: NT4-SP3 Sequence Prediction
daemon@ATHENA.MIT.EDU (Mark Gansle)
Wed Sep 9 20:10:10 1998
Date: Wed, 9 Sep 1998 17:31:09 -0500
Reply-To: Mark Gansle <zeus@SHELL.ACADIACOM.NET>
From: Mark Gansle <zeus@SHELL.ACADIACOM.NET>
To: BUGTRAQ@NETSPACE.ORG
In-Reply-To: <19980909183137.1344.qmail@root.org>
On Wed, 9 Sep 1998 nate@ROOT.ORG wrote:
> It is very easy. Assume that you have a standard deviation of 3 in the
> sequence every 10 ms (Ivan Arce measured a stdev of 2.6942). This means
> that a single guessed sequence of 499, 500, or 501 has a ~68% (1 stdev)
> chance of being correct. Assuming you are guessing one every 10 ms, it
> would only take 3 tries (30 ms) for you to have a better than 90% chance
> of succeeding.
Just as a point of order, ~68% would fall between 496 and 502, assuming a
bell-shaped curve. Your numbers fell within a one-standard-deviation
interval, and 68% fall within one standard deviation (plus or minus) of
the mean (499, according to Ivan). Plus, I'd wonder if the distribution
is truly bell-shaped.
Regardless of this point, your argument is still valid. Chebysev's
theorem tells us that at least 75% would fall within a 12-unit interval,
which means that this is open to a not-so-brute force attack.
Mark Gansle
