From: Mike Lorrey (mlorrey@yahoo.com)
Date: Wed Sep 18 2002 - 17:24:15 MDT
--- gts <gts@optexinc.com> wrote:
> Mike Lorrey wrote:
>
> > One respondent said that while the keyboard method isn't truly
> > random, for all intents and purposes its results cannot be
> > distinguished from random, which kinda reminded me of the classic
> Clarke
> > saying about distinguishing sufficiently advanced technology from
> magic.
>
> I was the aforementioned respondent. It is true, without doubt, that
> pseudorandom number sequences can be generated that pass all known
> tests
> for randomness. However the question here is how one might generate
> genuine random numbers as opposed to pseudorandom numbers. There is a
> distinction to be made here between numbers that are apparently
> unpredictable but determined and numbers that are both actually
> unpredictable and actually undetermined.
>
> In principle, a determined but apparently unpredictable sequence can
> be
> cracked, even if the method necessary to crack the sequence would
> require an unrealistic expenditure of effort and resources, and/or
> require knowledge of initial conditions that are at present
> unavailable.
> A sequence that is both unpredictable and undetermined would on the
> other hand be uncrackable even in principle.
The problem is that such nondeterminism makes it entirely useless for
encryption. If you cant decrypt something (i.e. via a deterministic
algorithm), then you are wasting your time. Adding plaintext to a
unpredictable and undetermined keystream via some deterministic
algorithm renders a ciphertext sequence that is non-random,
deterministic, and is therefore as attackable as one encoded via an
unpredictable determined keystream.
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