Re: Cryptographic strength in Wireless Alarm Systems?

"Mark Lomas" <sp@m.not.wanted> wrote in message
news:NL-dnT2M28k1tMjZRVnyrg@pipex.net...
|
| "Richard Herring" <junk@[127.0.0.1]> wrote in message
| news:xIBilpKPI1TEFwkc@baesystems.com...
| > In message <-eadnXVRn4acNtPZRVn-gA@comcast.com>, "Ed Weir (ComCast)"
| > <Anon@Maus.duh> writes
| >>"Richard Herring" <junk@[127.0.0.1]> wrote in message
| >>news:K2+MaSJ3NLSEFwp7@baesystems.com...
| >>| In message <444797cc@dnews.tpgi.com.au>, David Eather
| >>| <eather@tpg.com.au> writes
| >>| >Ed Weir (ComCast) wrote:
| >>| >> "David Eather" <eather@tpg.com.au> wrote in message
| >>| >>news:44462c4a@dnews.tpgi.com.au...
| >>| >> | Ed Weir (ComCast) wrote:
| >>| >> [snipped]
| >>| >>
| >>| >> | I don't understand your argument. It is possible to make a
spread
| >>| >> | spectrum wireless alarm secure or make it insecure, which seems
to
| >>be
| >>| >> | the same situation as an alarm using a fixed frequency - so what
| >>exactly
| >>| >> | is your point with SS.
| >>| >> The relative impracticality of jamming a spread spectrum vs.
jamming
| >>| >>a fixed frequency.
| >>| >> - Ed.
| >>| >You mean a nill difference don't you. It does not take much effort
to
| >>| >design a transmitter that put out noise all over a defined spectrum.
| >>|
| >>| That's only necessary in the linear regime. Unless the receiver can
| >>| handle an infinite dynamic range, any sufficiently strong signal
within
| >>| its bandwidth can drive it out of linearity and effectively block it.
| >>|
| >
| >>Yeah - right. http://spincom.ece.umn.edu/shengli/spie01.pdf
| >
| > Nothing there about nonlinearity of the physical layer. They're only
| > considering additive noise and interference.
| >
| > Ideal linear radio receivers don't exist. Especially wideband ones. Ask
| > any RF engineer.
| >
| >>(Some nuts are just plain numb...)
| >>
| >>If you really want to know more...
| >
| > Wrong layer. It doesn't matter how clever your coding is, if the
receiver
| > can't hear it.
| >
| >>http://www.tapr.org/ss_intro.html
| >>
| >>If you want to try jamming something for the fun of it (and test your
| >>hypotheses)
| >>http://www.dmartstores.com/ge27730ge2ad1.html (use a Faraday cage or
don't
| >>drop the soap)
| >>
| >>All goooogled with [jamming digital spread spectrum]
| >>- all a great deal harder than you thought.
| >>
| >>Well, there you go.
| >>Cheers,
| >>- Ed.
| >>
| >
| > --
| > Richard Herring
|
| Why all this discussion of jamming? Surely the sensible way of designing
an
| alarm is to use absence of a signal as the trigger.
| I would expect each component to broadcast a heartbeat signal that stops
| when the component wants to signal an alarm.
| A jamming device would also trigger the alarm by preventing receipt of the
| heartbeat.
|
| Mark

So when the alarm is finally turned off, the jammer strikes, right?
Uhhhhhh... ooopsie

Hey put me down for one of those right away!
Received on Mon May 1 02:06:37 2006