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[aprssig] Authentication over APRS was: Ab)Use of APRS for telemetry? Anyone doing it?

Robert Bruninga bruninga at usna.edu
Mon Dec 6 17:10:10 UTC 2004


Good idea.
Yes, have the "meaning" in public domain and only 
authenticate the "signature".   I would think that that
would be within the spirit of the FCC rule.  I am sure
the FCC would be all in favor of making it harder for
LIDS to abuse amateur radio... by allowing for signed
transmissions!

>>> washer at trlp.com 12/6/04 10:43:06 AM >>>

This brings up a question I've had for some time. As I recall, the FCC
rules prevent amateurs from using "encryption" or anything that obscurs
the meaning of a message. I don't recall the exact words.

But what if I wanted to have a secure method for sending commands ( to
non space based devices, as I seen to recall the FCC made an exception
for satelite control)?

Including a simple password in the message does nothing to prevent
"replay attacks" (not good if you want to do something like open your
garage door, or unlock something)

One could certainly use a OTP (one time pad), but that clearly violates
the FCC rule mentioned above.

So, I was thinking the best method would be to send the command in
plain text, thereby making the FCC happy. Including a date stamp to
avoid replay attacks. And finally, attaching a hash of the message body
encrypted with a PK (public key) tool. This way nothing is encrypted
excecpt the "signature".

I've not given this much thought as to the "size" of the key, and the
complexity of PKE code for microcontrollers...

Has anyone else thought about this? Any great ideas?

 - jim

p.s. If you all think this is way over the top, you are likely
correct.. but I worry a lot about encryption for networks, etc at my day
job.

On Mon, 6 Dec 2004 07:17:08 -0800
<scott at opentrac.org> wrote:

>
> I haven't seen the KPC-3+'s password-protected I/O feature.  I'll
have to
> check that out.  Though no TNC I've seen yet has had any kind of
strong
> authentication.
> 
> Scott
> N1VG
> 
>

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