On Mon, 29 Dec 2003 06:26:53 GMT, Chad Irby wrote:

In article ,
ess (phil hunt) wrote:

Are all of them easy to degrade? Even spread spectrum or frequency
hopping ones?

You should remember that "spread spectrum" is not synonymous with
"unjammable" or "undetectable." As far as that goes, some wideband
jamming techniques can be very effective against normal spread spectrum
communications. There are some major limitations that come with spread
spectrum, mostly having to do with power versus range versus noise.

Frequency hopping is pretty good for keeping people from hearing what
you're saying, but once you know the general band they're working on,
you can either jam them with suitable wideband frequencies, jump on
their frequencies before the receiver can lock on ("fast" jamming) or a
number of other moves.

You can defeat these ECM moves, but the counter-countermeasures cost a
*lot* more money than the countermeasures. And, once again, you're
getting into a technical war with a country that spends a *lot* of money
on that sort of thing.

A quick perusal of some webpages on the 802.11 wireless spec suggest
that the direct sequence spread spectrum is probably the more secure
of the two possibilities (frequency hopping is the other possibility).

However, the fairly modest processing gains - only about 10db or so
according to:

http://www.wireless-nets.com/article...per_spread.htm

and the relatively modest and specific bandwidth allocations

902-928 MHz
2.4-2.4835 GHz
5.725-5.850 GHz

suggest to me that digital internet systems based on the 802.11 spec
will probably be relatively easy to jam or detect, especially if the
receivers and transmitters are using low-gain antennas ("isotropic").

It also seems to me that the need for routing signals through multiple
"hops" is going to

1) be vulnerable if any intermediate system is compromised
2) require routing information to be propagated through the internet
which will identify active sites.

There are some other interesting questions, like what the procedure
for adding a node to this internet system is.