On 6/23/2010 10:04 PM, ra3apw wrote:
Thank you All for answers and clarifications.
Really the key word of my question was _AIR interface (RF) authentication.
_Do we have a procedure to implement this feature (air interface
authentication) in D-Star?
For radio digital protocol it should not be difficult technically.
73, Karen
RA3APW
__._,_.__
??????? Karen,
There is nothing in the protocol to support authentication, it only
provides identification. Current generation radios implement the
standard and that standard has no mechanism for authentication.
Authentication would have to be an add on application and for current
radios, that would mean some form of external device to handle the
authentication mechanism. Any true authentication would have to have an
irrefutable token, probably some public/private key mechanism with
distribution of keys to licensees off the air (e.g. via secure Internet
transfer). In some countries it may be problematic to use such an
authentication system since it might include an encrypted token between
radios and some countries forbid encryption on RF, though this might be
considered a control signal. Such a system also would be fairly
impractical because of database size and updates for mobile stations.
You can't depend on a network based authentication service as such an
extension would, by definition, have to support simplex transmissions
off the network.
For most of us, there is no need for such a system as this is amateur
radio, a hobby, and largely self policed. There are regulations that
can support prosecution of those who choose to abuse the hobby. For
example, in the US it would be very easy to say that anything other than
the operator's station callsign in the "MYCALL" field of a D-STAR signal
would be a false identification, which is expressly forbidden in the US
Regulations 97.113a(4) "...messages encoded for the purpose of
obscuring their meaning, except as otherwise provided herein; obscene or
indecent words or language; or *false* or deceptive messages, signals
or* identification*;" -- regulations in Russia may be different. There
will always be callsign pirates and those who do not identify at all,
and weak authentication just will encourage increased anti-social behavior.
At the repeater/gateway level, it would be fairly easy to filter out
calls that don't have recognized callsigns. This should probably be
implemented. I have written a regex (Regular Expression) filter that is
pretty effective in finding patterns that look like amateur callsigns or
one could implement a filter that checks a database of callsigns (such
as the G1/G2 registration system), but none of these prevent pirates.
One hazard of such a filter is bit loss in the address fields creating
an unrecognizable callsign, which would be rejected for an otherwise
legitimate transmission, with no feedback to the transmitting operator
who may speak for an extended period.
I support a no pre-registration approach. A new user should be able to
buy a radio, program MYCALL, and get on the network from RF (network
connected devices are another story). This means either the filter has
rules of what a MYCALL should look like, or have automatic lookup of any
and all callsigns issued -- pretty easy to do in countries like the US
where the license database is a public record and freely distributed
(with daily updates) but may be nearly impossible in countries where
such data is not freely and regularly available.
So "technically" solutions could be derived, but from a regulatory,
D-STAR standard extension, and pragmatic point of view, this may be very
difficult.
--
John D. Hays
Amateur Radio Station K7VE <http://k7ve.org>
PO Box 1223
Edmonds, WA 98020-1223
VOIP/SIP: [email protected] <sip:[email protected]>
Phone: 206-801-0820
801-790-0950
<mailto:[email protected]>
