Re: SETI: SAT Spread Spectrum indistinguishable from normal

Michael M. Butler (mbutler@comp*
Mon, 10 Nov 1997 01:26:07 -0800

All the counterpoints are well taken. Plus, even if you could determine that
the "noise" exhibited some slight autocorrelation or other statistically
significant deviation from randomness of the kind you expect (e.g., gaussian),
it doesn't mean you could decode it. For all we know, pulsars are modulated,
too, and we've come up with the naturally-occurring starquake as an explanation
when the truth is that They are doing it.

Re: optical spread spectrum, I seem to remember either inventing or hearing
about a trick with quantum wells that ought to let you create something very
like a free-electron laser.

I nicknamed this a "caged-electron laser".

These ought to be insanely efficient and might even be structurable as phased
arrays, active countermeasures like the ones rumored to be in place on the B-2
and FB-117*, etc.

* I forget what that technology is called; it's the one where the material
itself is primed and constructed with wideband rectifiers, dipoles, and other
circuitry peppered through its bulk so as to return a spoof signal with zero
processing delay--anyone out there remember the name of it? ...only on the nano

BTW, Crit is up, and it rocks.

Steve Witham wrote:

> I think it is necessary to have redundant information for clock syncing and
> error recovery. But, if the things we believe about cryptography are
> true--that there are "hard problems", for instance--then the overhead can
> be small and the result can still be impossible to distinguish from noise--
> even though there is redundancy, it's a hard problem to see it.
> There is that funny comment in A Fire Upon The Deep where (as we the
> readers are being treated to a boring slow-motion chase across the
> galaxy) two characters pass the time by debating the feasibility of public
> key cryptography (or any scheme except one-time pads generated with true
> randomness)...
> Quantum stuff throws wildcards into predictions about computability &
> also provides quantum crypto possibilities, so things could look different,
> even pretty soon.
> But as far as I know you can make redundant information look like noise.
> (later) Oh, PHIL started this thread!?
> Also, like Phil says, you can make your signal have any spectrum you want
> and probably be sloppy about things that people with only terahertz
> technology can't detect--if they're who you're trying to hide from.
> *The Diamond Age* had those nanites with light-wavelength communication
> that appeared as colored sparkles. You don't have to actually wiggle the
> nuclei to control photons. Light waves are pretty long in nanometers--
> ~600-1200nm?
> I guess interstellar stealth will be
> mainly developed to hide from *local* enemies--people from your own
> planet with technology similar to or somewhat better than yours.
> You could extend "Good fences make good neighbors" to "Interstellar
> civilizations only spread as far & fast as their crypto technology
> makes safe from internal corruption." (Which is verbose but you
> could probably pack it into <1024 bits.)
> I hereby signify my recognition that this is science fiction based on
> science fiction.
> --Steve
> --
> Steve Witham under deconstruction
> "...when activated, it pops a message off the bag
> and recurs with the tail of the bag."
> --Vijay Saraswat and Patrick Lincoln

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