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I have some Retevis MURS two-way radios model number RT27V. In the programing software there is an option for DCS encrypt.

MURS programming software, showing DCS encrypt option

Now I turned on and off the DCS encrypt option and using my NooElec SDR with SDR# I can see the DCS tone with DCS encryption OFF. With DCS encryption ON I don't see the DCS tone in SDR# which makes sense since the DCS tone was encrypted.

So my questions are:

  • What kind of encryption would be used to encrypt the DCS tone?

  • And how can I see and analyze the coded squelch in SDR# or some other equivalent software for an SDR?

I'm thinking the encryption used is plain old XOR. I know a good majority of wireless computer keyboards use XOR for encryption, so I'm thinking in the realm of keeping it simple for electronics, this too may be XOR. In order to confirm this I'd have to see the carrier squelch somehow in SDR# or some other program. There is a web-like program at Github called Cyber Chef that I may be able to use with this to decode the digital string.

Thanks in advance.

PS: Keep in mind this DCS encrypt option in the software is NOT turning on and off DCS. That option is the QT/DQT option you see in the software pictured in the link above. This DCS encrypt option literally encrypts the DCS tone. I never new about this technology myself until I bought this radio.

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    $\begingroup$ puh, there's a lot going on here. I'm taking relatively arbitrary bets that "encrypted DCS" isn't actually encrypted at all, but just something like a known spreading sequence or something. Then, marketing happened. $\endgroup$ – Marcus Müller Oct 8 '20 at 9:40
  • $\begingroup$ I shall ask the horse's mouth and see if I can get a reply. What I would like to do however is know how to capture the sub tone on a carrier in SDR# or some other SDR#-like program. $\endgroup$ – GhostProtocol Oct 12 '20 at 10:36
  • $\begingroup$ what's a "sub tone" $\endgroup$ – Marcus Müller Oct 12 '20 at 10:41

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