Astro Saber encryption key

[Securevoice]

Hi everyone,

I have being doing some recent tests with my Astro Sabers equipped with DES-OFB. I learned that when a personality is set up for IMBE and the Astro secure unmute rule is set to normal sq the radio will unmute on any known key regardless if a specific key has been strapped to the personality or not. I also found out that the recieving radio is being forced to switch to the same key as it recieves. This only for a few seconds then it switches back to either the strapped key or to the original user selected key. Is this feature a specific OFB thing? I take it that this will never get to work in 12kbit operation? Thanks in advance.

 

[Project25_MASTR]

It's a standard feature with OFB, XL, ADP and AES-256.


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[Securevoice]

Thanks for the reply. Do you know if the feature also supports 12kbit XL?

 

[Project25_MASTR]

I do not.

 

[RFI-EMI-GUY]

Thanks for the reply. Do you know if the feature also supports 12kbit XL?

I am playing with some Systems Sabers with DES XL and I recall a programming feature where the transmit key follows a received key. Sorry I cannot recall exactly what it was called. I am still on the re learning curve of this old tech. The help files were not to helpful.

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[Securevoice]

I also have a few SS with DES-XL and also some with Multikey Modules. I never got to fully crack the trickyness of the SS. Some say Indexing is the key to the feature you´re refering to. There are some variations of 12kbit which has a similar feature. Having the radio set for scan would then force the loaded keys to be scanned. This option probably dosn´t reply to P25 and the commonly know encryption types. If you dig into SS again plz let me know.

 

[Securevoice]

So I finally found out the 12kbit does have the same feature of shifting keys. Don´t know about other radios like the Jedi series but my Astro Sabers now do shift keys in 12kbit mode as well. Basically it seems to work the exact same way as with P25 except that in 12kbit mode the transmitting radio uses MDC1200 as a reference as to where recieving radios should look for the key. That´s where the key index comes in and I actually didn´t change anything in the indexing as the old set up already had index on the KVL. So what I did was to migrate Securenet (there´s an option next to the CKR field in the CPS) and left the CKR field disabled as the index already seemed suitable in my case. As far as I understand the CKR is more an APCO25 thing (something PS users wanted to keep track of the many indexes that may excist across states/nation). Only disadvantage as I see it is that you will have to live with the MDC1200 burst at the beginning of every secure transmission in 12kbit mode. I use a repeater most of the time and the Base station then switches between analog and CVSD re-clocking on every relaying (then disables the FM modulator after a second) which actually seems to be no problem so far I mean practically (of course it works) as I was worried it would be annoying as hell.
Besides the advantage of having different keys to intercommunicate with out having to pre-call using analog transmissions it certainly improves security when using more than just one single key per channel. The keys now kinda roll in an unpredictable pattern as users don´t have to use a specific key anymore. There may be some security issues although depending on the way the keys are being used and how different radios (levels of users) are being programmed. If a higher ranking radio has a shared key and a lower ranking radio uses this key on a given channel the higher ranking radio then will shift to this key as it recognizes it in the key index list despite the users previous selection of key. An immediate callback then forces the higher ranking radio to use the same key (the shared key) which may or may not make sense depending on the circumstances. Otherwise the higher ranking radio will have to wait 2 sec before next transmission (it then uses the Op-select key or the key being strapped in the CPS to the given personality). That´s where educating user in any Organization becomes vital in the attempt to understand how this works. When used properly it´s actually very useful tool.

 

[RFI-EMI-GUY]

That is pretty neat. I wonder if there is a system planner document that describes these features.

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[Securevoice]

Beats me