encryption and the new gre

[wwhitby]

But you can never hear ProVoice ever - so why does it matter?

Just because we can't hear it doesn't mean that we don't want to know what talkgroups are using ProVoice and are active. With the mixed mode system I listen to, at least 1/2 is ProVoice. Unless you have a scanner that will pass the digital audio through, or use Unitrunker, you will be in the dark about 1/2 of the system. You may not be able to hear what is going on, but you will at least know that those talkgroups are active.

I want to be able to see the activity on a trunked system, not just the activity I can hear. I'd rather have the ability to lock out what I don't want, then to have the ability taken away from me. Let the each scanner owner decide what is best for them!

That sort of info sounds like something appropriate for a PC.

Not everyone uses or wants to use Unitrunker for whatever reasons. Even though laptops are smaller then desktops, you can't carry one around with you attached to your belt.

Besides, I still believe its only a matter of time before someone comes out with a bootleg, third-party DSP upgrade that will decode ProVoice. Legal, no. But when its out on the web, the genie won't go back into the bottle.

Warren

 

[TPKeller2]

Besides, I still believe its only a matter of time before someone comes out with a bootleg, third-party DSP upgrade that will decode ProVoice. Legal, no. But when its out on the web, the genie won't go back into the bottle.

A matter of time... sure. How long do you plan to live?

I know very little about ProVoice, but Google found this pdf for me, which says that they use either DES or AES for their encryption.

Now DES has proven to be vulnerable with modern day hardware, with the most recent solution being a very specialized device called COPACOBANA, which according to Wikipedia, costs about $10,000, and takes on average 6.4 days to break, with the worst case being 12.8 days. (It's brute force, so on average you find the key in half the time it takes to try all possible key combinations.) Of course that is assuming they don't change the key. Moore's Law has for all practical purposes, killed DES for critical security applications. Given time and money, you could record the transmissions and eventually decode them, but it would be virtually impossible for you to do this in real-time, assuming they do change the keys every once in a while.

AES has no practical solution at this time.

Perhaps it would be helpful for you to do some reading up on encryption. The algorithms can easily be incorporated into the DSP, obviously this is how the ProVoice radios work. It's the key that is the problem, and while some day, these standards may be found vulnerable to the primitive hardware that a hobby scanner can afford, you can certainly be assured that by then the authorities will have long upgraded to new encryption methods that will always remain beyond the reach of the general public. I'm sure that hobby scanners are way, way down on the list of "unauthorized" folks who are very interested in finding solutions to break these encryption algorithms!

Theron

 

[wwhitby]

Perhaps it would be helpful for you to do some reading up on encryption.

I'm not talking about decoding any form of encryption, i'm talking about decoding ProVoice digital modulation, which isn't encrypted. From what i've read, ProVoice digital uses the same chip that APCO-25 systems use, however the algorithm is different.

So, I still think its a matter of time before ProVoice is demodulated.

Warren

 

[TPKeller2]

I'm not talking about decoding any form of encryption, i'm talking about decoding ProVoice digital modulation, which isn't encrypted. From what i've read, ProVoice digital uses the same chip that APCO-25 systems use, however the algorithm is different.

So, I still think its a matter of time before ProVoice is demodulated.

Warren

Ah... as I started out, I know very little about ProVoice. Can anyone point to any reference material that would help someone (me) get up to speed?

The pdf I mention in my earlier post is for a particular radio, but has this blurb:

"The M7100IP supports the EDACS Security Key (ESK), which is an EDACS/ProVoice feature. ESK prevents unauthorized users from programming radios for use on and from accessing an EDACS or ProVoice system."

which doesn't say it's encrypted (and encryption is mentioned elsewhere), but sure sounds like they are using some sort of a key algorithm to keep folks from decoding the stream.

Theron

 

[jpryor]

My new PSR-500 is not stopping or unmuting on encrypted P25 talkgroups that are active on the Ohio MARCS system (Motorola 3600 baud Digital only system). I have not heard how it works on other types of P25 encryption yet (conventional, true P25 systems).

 

[scan-pa]

My 500 does break sq. on any Talkgroup that uses ProVoice Digital Modulation while doing a wildcard tg search.

Works great on the Analog FM modulation talkgroups however.

great scanner.

 

[kikito]

Maybe i'm in the minority, but I want to see everything that is happening on a trunked system. I hope GRE DOESN'T change this. Now, for the first time, you can see ALL system talkgroup activity, instead of only what is analog.

To keep everyone happy, hopefully they'll make it not only a selectable (on/off) option but also a choice of global or per object option.

 

[kikito]

From what i've read, ProVoice digital uses the same chip that APCO-25 systems use, however the algorithm is different.

So, I still think its a matter of time before ProVoice is demodulated.

Warren

Yeah, P25 and ProVoice do use the same vocoder even (IMBE), however, ProVoice uses 4-slot TDMA instead of P25's Phase 1 current FDMA. P25 Phase 2 will be using TDMA.

EDIT: Nevermind about the TDMA part on ProVoice, I think that's used only it's "cousin" OpenSky systems....

 

[rdale]

Why not start a new thread on ProVoice? Oh wait - there are hundreds of posts already showing you why it won't ever be monitored.

On the encryption note, just as in the Pro96, it will mute 3600 baud encryption but not 9600 P25.

 

[mancow]

I thought it was AMBE.

Anyway... it's all a matter of DSP coding but it's a moot point.

Yeah, P25 and ProVoice do use the same vocoder even (IMBE), however, ProVoice uses 4-slot TDMA instead of P25's Phase 1 current FDMA. P25 Phase 2 will be using TDMA.

EDIT: Nevermind about the TDMA part on ProVoice, I think that's used only it's "cousin" OpenSky systems....

 

[kikito]

I thought it was AMBE.

I think OpenSky uses AMBE and ProVoice uses IMBE.