Encrypted Audio

[brscanning]

Could anyone tell me if the attached audio sample is an encrypted signal or simply my scanner's failure to properly decode the signal? I was under the impression that encrypted signals sounded like static. The sample is from Louisiana's 700 MHz P25 system. I can sometimes hear one side of the conversation while the other side sounds like the sample audio.

Another question is whether the encryption is controlled from each radio? For example, can one side of the conversation be encrypted while the other is not?

 

[scannerfreak]

That is digital encryption. If enabled, the user can manually switch between clear and encrypted modes. So, in your case if hearing only one side in the clear, one side has the switch flipped and the other does not.

 

[WayneH]

All a radio needs is the key loaded and it automatically decrypts regardless of the radio's settings.

There are more complicated examples with multiple keys but that's the gist.

 

[specialforces]

Yes that is encryption.

 

[brscanning]

Thanks for the replies. I suspected it was encryption since it was consistent. My doubts came from a couple of statements I found on the web that encryption sounded like hiss or static. I have even heard a sample of an encrypted signal that did indeed sound like static.

 

[WayneH]

Thanks for the replies. I suspected it was encryption since it was consistent. My doubts came from a couple of statements I found on the web that encryption sounded like hiss or static. I have even heard a sample of an encrypted signal that did indeed sound like static.

That's the older 12kbit analog encryption commonly referred to as SecureNet. It's a rush of static/squelch with a beep at the end.

 

[fourthhorseman]

curious,,
i hear that sound alot here in philadelphia-apco-p25,
the same exact audio in fact...

i hear dispatch radio back with replies that the transmission
is unreadable..
i always thought it was poor signal/poor decode of the digi stream...

the officer usually cuts back in and is choppy-mostly clear after dispatch
advises that its a poor signal..

very informative..