Looking for help understanding Encryption data on DSDfme

[Frasso]

Hi, i'm playing a bit with DSDfme.
Someone can help me to understand what it is show?
I know that RC4 is an algorithm for encryption, but that's it.

The "MI:" keep changing while there is voice in the channel

On DSDplus it says ALG=RC4 KeyID=1

 

[TheButcher]

ARC4 aka Enhanced Privacy encryption. Without the key, you can't listen in.

 

[Boingel331]

The data is encrypted using a radio's RC4 key number 1. The number that keeps changing is RC4's Initialization Vector (IV) Motorola calls it the Message Indicator (MI). Its random nature is what gives the encryption process for each frame randomness.
What protocol are you decoding?

 

[Frasso]

The data is encrypted using a radio's RC4 key number 1. The number that keeps changing is RC4's Initialization Vector (IV) Motorola calls it the Message Indicator (MI). Its random nature is what gives the encryption process for each frame randomness.
What protocol are you decoding?

It's DMR, probably Hytera

 

[racingfan360]

It's DMR, probably Hytera

Assume you know how to generate log.ans from dsd-fme. I don't recall if it's visually possible to distinguish between Hytera Full Encryption (RC4) and Motorola EP (RC4) in simplex mode, but in Repeater mode Motorola EP and any other DMRA compliant radio types will generate a MI/PI Header (ie Slot 1 DMR PI H- ALG ID: 0x21 KEY ID ). Hytera won't.

 

[ki4hyf]

The "MI:" keep changing while there is voice in the channel

It will. And it isn't random.
The Next MI is: 0x1FBDACED
The Next MI is: 0xAEE9625F
The Next MI is: 0xBBBDCDFF
The Next MI is: 0xABFD4BAE
The Next MI is: 0xFAE9BFBB
The Next MI is: 0xAAF83097
and so on. There is a detailed thread on this: Motorola IV Calculation

 

[Frasso]

Assume you know how to generate log.ans from dsd-fme. I don't recall if it's visually possible to distinguish between Hytera Full Encryption (RC4) and Motorola EP (RC4) in simplex mode, but in Repeater mode Motorola EP and any other DMRA compliant radio types will generate a MI/PI Header (ie Slot 1 DMR PI H- ALG ID: 0x21 KEY ID ). Hytera won't.

Ok, I didn't know that, thanks.
I said Hytera because even if I cannot listen in to them, i know that 99% they're using hytera radios, at least on the field. Maybe the repeater itself it's Motorola.
Here in Italy there are a lots of systems that are hybrid between hytera, Motorola...etc

 

[Frasso]

It will. And it isn't random.
The Next MI is: 0x1FBDACED
The Next MI is: 0xAEE9625F
The Next MI is: 0xBBBDCDFF
The Next MI is: 0xABFD4BAE
The Next MI is: 0xFAE9BFBB
The Next MI is: 0xAAF83097
and so on. There is a detailed thread on this: Motorola IV Calculation

I'm honest...it's difficult for me to understand, but many thanks!

The last thing that I don't know is what ALG ID 0x21 means

 

[ki4hyf]

The last thing that I don't know is what ALG ID 0x21 means

AlgID 21 is DMR EP/RC4. Anytone's DMR RC4 AlgID is 1.