From: dougb@casbah.acns.nwu.edu (Douglas Bank)
Subject: Re: "I can't talk about that on the radio"
Organization: Northwestern University, Evanston, Illinois
Distribution: na
Date: Thu, 9 Apr 1992 14:10:33 GMT

In article <1992Apr8.172342.3944@vlsi.louisville.edu> meharp01@vlsi.louisville.edu (Michael Harpe) writes:
>
>OK, since you pointed it out in your .sig, I have a couple of questions that
>i'm sure are of general interest :-).  I understand that you can't reveal  
>proprietary information, I hope these questions are general enough.

Gee, I'm not sure what's proprietary and what's not.  I'll pretend I'm 
an ignorant salesman and answer what I can.
>
>1.  What encryption standard is employed in your system?

Many.  It depends what kind of system is bought.  DES is a common
method, but it is not easily exportable.  Motorola also supplies at
least two other proprietary algorithms that can (I think) be exported.
There are also algorithms suitable for classified traffic. 

>2.  What general security level can they reasonably expect?

very good security.  DES used to be OK for classified traffic.
Another algorithm is approved for classified traffic.

>3.  Are the number of keys sufficiently large to prevent me from purchasing
>    a compatible HT and trying to guess the key?

HT?  Do you mean the portable or something else?  Anyway, lets just say 
that the number of keys is way, way more than 1 trillion.

>4.  Are the keys easily changed or does it require a programming unit?

Motorola sells another product to load keys into a radio.  However,
they have been selling a new system where that isn't the case.
No radio I know of can enter keys into itself.  I guess the theory is
that you can't really trust the cops not to goof something up.  I'm
not sure.  
>
>I guess these are the kind of questions I would ask if I was considering
>purchasing a secured radio system.  Along those lines, what's to prevent
>"bad guys" from buying the same system?  Does Motorola have business 
>policies about who they sell secured systems to?

If you don't have the key, then you don't have squat.  It is probably
easier for the bad guys to steal the key than to break the system.
Of course, we try to make that almost impossible.  Then again, the
bad guys can always buy their own system to keep the cops out of their
communications.  As far as business policies go, we do what the feds
tell us to do.  We cannot sell DES to certain countries.  The classified
stuff can only be sold to certain groups.  I would think that even the
weakest digital encryption would be good enough for Guido's Pizzeria. ;-)
>
>BTW, I misspoke in my original posting on two points.  The tactical radios
>are the only ones that have converted (they have a 5 channel system, 4 of
>which are still "clear") and they use GE "Voice Guard" radios.  How does the
>Motorola system compare?  They use these radios through their standard 
>repeater system.
>
Ick, GE!  The competition.....  Our systems are not compatible.  Our
systems (now) use CVSD to encode the analog voice.  GE uses a sub-band
encoder that make the people talking sound like they are underwater.  I 
have a radio in my car (basically a scanner, but I can talk back ;-), that
isa, I can talk back if I want to go to jail) and I was suprised just how
many cops out there don't use encryption.  The only frequency that I found 
coded trafiic on (besides Motorolas) was an FBI frequency.

>It's great to have a "pro" in this group.  Maybe we can all learn more about
>communications systems while we exchange information.
>
>Mike Harpe, N4PLE
>University of Louisville
>
Say, do they still have those nasty black squirrels on campus?  I seem to
remember a couple of albinos too.


-- 
Doug Bank                       Private Systems Division
dougb@ecs.comm.mot.com          Motorola Communications Sector
dougb@nwu.edu                   Schaumburg, Illinois
dougb@casbah.acns.nwu.edu       708-576-8207