Re: SETI: SAT Spread Spectrum indistinguishable from normal

Steve Witham (
Sun, 9 Nov 1997 22:13:32 -0400

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

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--

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 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