pervect wrote:

:From my POV, the key point that I missed in my earlier post (the one
:you just replied to, there have been a bunch since then) is that GPS
:is spread spectrum.

Which really doesn't buy you much in the way of security. DS-SS
merely makes it easier for the receivers to do ranging functions.

:Of course this has spawned yet another argument, where I point out
:that if you know what the satellites are supposed to be sending, use
f encryption (rather than spread spectrum) would be unlikely to
rovide much security. Other people have suggested that "good codes"
:are harder to break than this. I haven't gotten around yet to
ointing out that all you'd have to do given that you would already
:have the plaintext because you know what the satellites have to be
:sending is to broadcast a signal that would provide a "lookup table".
:Then someone else could point out that this would slow the response
:time of the GPS system down. Then I could say, yes, but is that
:really significant. And the argument could go on for quite some
:time....

It's actually easier than this (since figuring out what the plaintext
ought to be is NOT as trivial as you make out). Just use DGPS and
hope they don't take down your differential station(s).

--
"Millions for defense, but not one cent for tribute."
-- Charles Pinckney