From: hal@venus.mitre.org (Hal Feinstein)
Subject: Re: Motorola 'Secure-Clea
Organization: Mitre Corporation, McLean, VA
Distribution: na
Date: Wed, 6 Jan 1993 22:57:44 GMT

In article <1993Jan6.133347.310@clark.dgim.doc.ca> nur@mars.dgrc.doc.ca writes:
>In article 7026@netcom.com, rcain@netcom.com (Robert Cain) writes:
>
>What about the modern analog devices that use split band inversion where
>one of 32 programmable split points in the voice band may be selected
>and changed at 60 Hz or faster at "random?"  Two separate inversions
>are performed, one for the lower sideband and one for the upper
>sideband around the split point.  This seems *much* harder.  This topic


These analog voice systems are considered really difficult to break.
The main market for these devices in the public service including
local and county law enfrocement.  The main problem is NOT that 
professional crypies are going to listen in but rather that the
local bad guys don't use their bearcat scanner to find out where the
police are. Another reason is that in small towns the local mayor
likes to listen into what the town cheif of police is up to and that
makes them unconfortable.  

Voice inversion is considered suitable for only keeping the uneducated
scanner crowd out.  When local law wants privacy they usually use 
something better then rolling code or voice inversion with fixed 
split bands.  The ones I've used were made by a company called
Transcript and they seem to use a combination of rolling code
and segmented voice time chip shuffling both under a key. 
Costs about $400 per radio installed. I don't know what the 
time epoch is for the shuffling but it couldn't be all that long.
Breaking this is usually more trouble to a local crook then its
worth to him.  Now if you don't like that you can go to the 
Motorola DVP system (CVSD voice encrypted with a bunch of non-linear
shift register [I think!]) or their DES voice system. Most serious
law types, meaning SWAT teams, couternarcs, the feds all use
the more serious MOTOROLA digital offerings.  If your crooks will
blow your brains out if they even hear white noise on the local
scanner channel then frequency hopping spread spectrum is the next
stop in sophistication  for law enforcement. I tested a bunch 
and for the FH systems, nothing shows up on local scanners. 
But again, if your crooks have the right gear they'll see the signal
jumping around when you get close-up. I tried a few FH systems for
security. One ran about 25 hop/sec. and despite the makers claimes
I both saw and heard it on my receiver. At the high end we used a
400 Hops/sec system operating in the low UHF band. Funny, the grass rolled
off the spectrum analyser just as we moved about 1000 ft from the 
facility fence. That was impressive.  There are also direct sequence
system but they get a bit spooky.

Now, I did have a chance to see what the real people use at a
certain military idustrial company. It was very far advanced from
the stuff I've just described. Not even in the same league. But,
its also moonshot prices. So I don't feel all bad. 

No, the analog "scrambled"  radio's can't stand up against offline processsing
even by an amateur with a reasonable tape recorder and a
low priced Motorola 56000 or Texas Instruments 32000 digital signal processing
board to play with. Software to do most of the work
is available usually over dial up BBS too. (Mr Bub for example)

tactical users can get away with scrambling like transcript does
But real people use digital. Heck, even the local TV news stations in
Washington DC are using  Motorola DVP  to keep from getting "scooped."

board to play with. 

Newsgroups: sci.crypt