DSDPlus DSD & P25 KEYID

[AF1UD]

One of the police departments in my area has turned on encryption. I got a RTL SDR to inspect the traffic and found that there is a keyid associated with each transmission. What is it and why does DSD give the output for it?

 

[caphab1]

Figure this thread might give some answers for what you're looking for.

KeyIDs in DSD+

Using DSD+ to decode encryption KeyIDs on Motorola and P25 systems, it typically displays a five-digit number. But the key IDs are 1, 2, 3 or 4 digit. How does the KeyID shown by DSD+ convert into the actual key id? Tks!

forums.radioreference.com

 

[AF1UD]

So... it's the challenge key for the radio with that ID to be authenticated?

 

[caphab1]

So by my gathering, all radios on the network have a list of a certain number of keys programmed, the transmit radio picks one and broadcasts it to the rest in use so they decode the ENC transmission.

 

[maus92]

The keys are stored in the radios. The KeyID is telling the radio what key to use.

 

[AF1UD]

So is it using key 4128 or keys 4, 1, 2 and 8?

 

[Kazzaw]

Using key 4128.

Basically, when someone transmit, the radio sends out a message saying ' We're using key 4128 for this conversation'. All the receiving units, providing they are programmed correctly will then use whatever key they have stored in 4128 to decode the transmission correctly

 

[cg]

It has nothing to do with the content of the Keys, rather is the "name" or index number of the key.

 

[boatbod]

To the OP: there's a Message Indicator parameter too. That's used along with the KeyId to select the correct encoding type and seed the crypt algo.

 

[AF1UD]

To the OP: there's a Message Indicator parameter too. That's used along with the KeyId to select the correct encoding type and seed the crypt algo.

Are you referring to this?

 

[dlwtrunked]

One of the police departments in my area has turned on encryption. I got a RTL SDR to inspect the traffic and found that there is a keyid associated with each transmission. What is it and why does DSD give the output for it?

It is the number of the key but not the key itself. Note that the number can be randomly picked by the system programmer and they do not need to be assigned sequentionally or in order. Note also that Al=AES means they are using AES encryption (as opposed to something like DES encryption). Sometime on a large system, it helps you understand the system as it can indicated what talkgroups or units can talk to others. In other cases, it might help figuring out is different frequencies are the same operation (but of course different operations may use the same key number just by chance).

 

[Outerdog]

Are you referring to this?

View attachment 121090

No. What you have displayed there is:

Encrypted Group call, talkgroup (TG=1), Radio ID (RID), Priority (Pro), Alg (Algorithm), KeyID (displayed as hex(dec)).

 

[SlipNutz15]

One of the police departments in my area has turned on encryption. I got a RTL SDR to inspect the traffic and found that there is a keyid associated with each transmission. What is it and why does DSD give the output for it?

How are you displaying that info? I'm trying to view the same info, it's decoding the system, but that information is not showing.

 

[Kazzaw]

I dont think there are any specific settings, it should just appear when an encrypted group appears

 

[SlipNutz15]

I dont think there are any specific settings, it should just appear when an encrypted group appears

For some reason when monitoring our system in PA it says encrypted TG, the TG number and unit number but not keys

 

[Jay911]

It's a feature in the new(est) versions of DSD+ Fast Lane, I'd say about the last 5 versions so you have to be pretty much up to date.

I believe your role has to be 1R (combined CC/VC) and you have to enable "Limited Encrypted Conversation Following".

I have my DSD machine apart right now or else I'd get you more accurate info, sorry.

 

[SlipNutz15]

It's a feature in the new(est) versions of DSD+ Fast Lane, I'd say about the last 5 versions so you have to be pretty much up to date.

I believe your role has to be 1R (combined CC/VC) and you have to enable "Limited Encrypted Conversation Following".

I have my DSD machine apart right now or else I'd get you more accurate info, sorry.

Yeah I downloaded the latest and updated my folder and it shows it’s an encrypted convo but no key data.

 

[BM82557]

Yeah I downloaded the latest and updated my folder and it shows it’s an encrypted convo but no key data.

For me Keyids show up in the Groups window --

 

[SlipNutz15]

For me Keyids show up in the Groups window --

View attachment 127092

I understand that but how do I view this window or is it the paid version only?

 

[cg]

it is in the Fast Lane version.
In a trunked system, you need to allow the secure group to be monitored as the key info is apparently read from the voice channel.