Good afternoon group
Hopefully someone can help me on this one. Our state police are about to invest in a P25 system and there is talk that it will be fully encrypted all the time. Damn !
Anyway, there is also talk that it will be a Conventional system and NOT a trunked system.
Does OTAR work on a Non Trunked System ? I was under the impression (and I may very well be wrong here folks) that it works only on a trunk system and the OTAR commands are fed as a part of the control channel stream.
Ie: on a conventional system does the normal channel open up and spit out a heap of digital signals to change keys etc etc if it does work on a conventional system ?
If it doesn't work on a conventional system, I can envisage problems when radios are lost/stolen etc etc in having keys changed ! After all an encryption system is only as secure as the keys and key rotations it is using..
Any thoughts appreciated
Thanks
Mike
New P25 System Coming & It Might Be Encrypted !!
Moderator: Queue Moderator
Otar can work on conventional systems.
If a radio is lost or stolen, a command can be sent from the radio system to "kill" the radio so that it does not function. This would apply to trunked to conventional systems if the option is purchased.
The radio's themselves can be programed to erase the encyption key if the battery is removed or if a password is entered incorrectly. There is no known way to retrive the encyption key from the radio.
If a radio is lost or stolen, a command can be sent from the radio system to "kill" the radio so that it does not function. This would apply to trunked to conventional systems if the option is purchased.
The radio's themselves can be programed to erase the encyption key if the battery is removed or if a password is entered incorrectly. There is no known way to retrive the encyption key from the radio.
Lowband radio. The original and non-complicated wide area interoperable communications system
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mrtor
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OK on that so it will work on a conventional system.Pj wrote:Otar can work on conventional systems.
If a radio is lost or stolen, a command can be sent from the radio system to "kill" the radio so that it does not function. This would apply to trunked to conventional systems if the option is purchased.
.
Now the other part of my question
In the case where an inner city channel may be running say 500 units and they want to change the encryption key, how is that achieved (is it as I describe above ?Ie: on a conventional system does the normal channel open up and spit out a heap of digital signals to change keys etc etc
Then, what happens if the unit is on another channel when the OTAR command is sent out, does the despatcher (or whoever) then have to send out the commands over and over again until everyone is back on air with the new key ?
If I am way off in grasping how this will work on a conventional channel, please enlighten me
Thanks
Mike
Re: New P25 System Coming & It Might Be Encrypted !!
G'day... I'll address these from the beginning as I ran out of time to reply yesterday
Not too sure about NSW, but I know that SA has a P25 trunking network, and the police are using encrypted Astro digital voice.
Welcome to the way SA and NSW have been doing it for a while (ok, maybe 12 months) nowmrtor wrote:Hopefully someone can help me on this one. Our state police are about to invest in a P25 system and there is talk that it will be fully encrypted all the time. Damn !
Not too sure about NSW, but I know that SA has a P25 trunking network, and the police are using encrypted Astro digital voice.
P25 generally refers to trunking. Are you saying that it's likely just conventional with encrypted IMBE (Astro) digital voice?Anyway, there is also talk that it will be a Conventional system and NOT a trunked system.
Yes, OTAR works on conventional channels as well as trunking. MDC has OTAR capability for when Astro is not in use (ie encrypted non-digital voice), as does Astro itself. OTAR isn't actually part of the trunking control channel.Does OTAR work on a Non Trunked System ? I was under the impression (and I may very well be wrong here folks) that it works only on a trunk system and the OTAR commands are fed as a part of the control channel stream.
BasicallyIe: on a conventional system does the normal channel open up and spit out a heap of digital signals to change keys etc etc if it does work on a conventional system ?
Correct. But there are plenty of tamper protection mechanisms that Motorola have engineered that if enabled make it very hard to capture and extract keys intact.If it doesn't work on a conventional system, I can envisage problems when radios are lost/stolen etc etc in having keys changed ! After all an encryption system is only as secure as the keys and key rotations it is using..
Pretty much... They'll either get rekeyed back at base with a KVL (handheld device that plugs directly into the radio), or they'll get the dispatcher to remotely rekey the radio when they realise that they keep getting decryption error messages on the radio.mrtor wrote:In the case where an inner city channel may be running say 500 units and they want to change the encryption key, how is that achieved (is it as I describe above ?
Then, what happens if the unit is on another channel when the OTAR command is sent out, does the despatcher (or whoever) then have to send out the commands over and over again until everyone is back on air with the new key ?
If memory serves...each radio in an OTAR system is initially loaded with what's called a shadow key. Its this key that allows the OTAR to work. The dispatcher can rekey the radio or the radio user can send a command from his radio to request a reload/new key. When the request is sent, the OTAR computer verifies if that is the proper radio and if that radio is still authorized for a new key.
Because of the shadow key and other safeguards, you cannot buy the same radio with the same options and have that radio properly OTAR.
Because of the shadow key and other safeguards, you cannot buy the same radio with the same options and have that radio properly OTAR.
Lowband radio. The original and non-complicated wide area interoperable communications system
And to clarify, the encryption key used for OTAR that Pj has mentioned, is only used for OTAR. This reduces the traffic over the air using this key meaning that you'll need a LOT (years and years) of OTAR requests before you can get enough traffic to even start thinking about deriving the key and being able to listen to the new keys as they're being broadcast.