Mystery Encryption

[kb2vxa]

Hi guys,

Here's a sample of encryption I never heard before. 155.475 being an interoperability frequency (SPEN 2) in NJ it's normally quiet but the other day there was a bit of tropo with signals coming in from New England. Two questions, what could be the source of the transmissions (mobiles are highly unlikely) and what sort of voice encryption could it be?

 

[kingpin]

It sounds to me like speech inversion on a nearby frequency like 155.4875 or 155.480 or something like that. Just my opinion...

 

[10-95]

Speach inversion. Any kind of High end encryption will not have anything close to intelligible audio. If you listen closely you can actually tell when the person or persons start talking.

 

[WayneH]

Someone, possibly CA DOJ, does the same thing on NALEMARS and CLEMARS here in the SF Bay Area. It's always surveillance activity.

 

[Joseph11]

I was hearing this too. It's rolling code voice inversion. It sorta made me think "wtf?" for a few seconds when I first heard it and saw what frequency it was on.

EDIT: BTW, SPEN 2 is a national police interoperability frequency.

 

[SCPD]

Definitely rolling code. You can hear the synchronization data bursts.

 

[kb2vxa]

Hi again,

I've never heard rolling code before so I guess that clears up the mystery, thanks. Later I expanded one of the ticks and found it to be a four cycle sine wave, definitely a sync burst. I haven't figured out just where it came from but I can say that many of those interop frequencies are used as police "secret channels".

 

[fineshot1]

Hi guys,

Here's a sample of encryption I never heard before. 155.475 being an interoperability frequency (SPEN 2) in NJ it's normally quiet but the other day there was a bit of tropo with signals coming in from New England. Two questions, what could be the source of the transmissions (mobiles are highly unlikely) and what sort of voice encryption could it be?

Sounds like aliens have infiltrated mother earth. We better break out those tin foil hats now.

 

[Declared_Hostile]

It sounds a bit different than the rolling code inversion that I've heard before. I suppose every manufacturer implements it a bit differently. This sample is a higher pitch, has less modulation and I believe the timing pulses are much faster and higher pitched. It's been a while though. I remember it being quite clear very well modulated with very little hiss and with a steady beat of timing spaced through the transmission. Very distinctive and it was hopeless to decode with a standard inversion descrambler. Not that I tried or anything. I just heard.

 

[kb2vxa]

Hi again,

Fineshot, if anyone should know about aliens in Ocean County it's me, I see them all over the place every time I go into town. (;->)

Hostile, it makes little difference what the pilot tone frequency is as long as it's in the audio band and above the highest speech frequency. I finally figured it out having been familiar with frequency inversion scrambling since the 70s when it was first introduced. It's generated the same way as an SSB RF signal only with audio, you can find a balanced modulator circuit anywhere. I built a decoder to listen to the PD when they went "yellow" so it's no big deal. Rolling code simply randomly selects a pilot tone to encode and sends a burst of it to a PLL circuit on the receiving end to keep the demodulator's pilot tone injection in sync with the modulator's, the tone changes with every tick.

Oh, perhaps I didn't mention the fact that the signals weren't strong enough for full quieting so there's a bit of a hiss on the recorded audio.

Now maybe some of you enterprising digital experimenters will research the 555 timer chip, an L-C wave shaping circuit, ring demodulator and a way to lock it in with the tone burst pulses. Here's a hint for you, with RF a product detector is used, look up the circuit.

 

[XTS3000]

I've used rolling-code inversion before. That audio file sounds like no rolling code Iv'e heard/used before.

The only thing that makes it sound like rolling code is the syncro packets, other than that, I don't know what it actually is.

 

[902]

I've used rolling-code inversion before. That audio file sounds like no rolling code Iv'e heard/used before.

The only thing that makes it sound like rolling code is the syncro packets, other than that, I don't know what it actually is.

I didn't look at it on any kind of analyzer, but it is likely a "split band" type of inversion where DSP filters components of the voice spectrum and then reassembles them in a certain manner.

The sync is faster than most after-market analog encryption devices.

 

[kb2vxa]

Hi again,

I think you guys are missing the point which is "rolling code" simply means the system uses a code key randomly selected (rolling) at intervals rather than one that is fixed throughout the transmission. Which type of baseband scrambling is used is irreverent when we're talking about code keys.

 

[Joseph11]

I'm receiving this again, in case anyone is interested in listening to it.

 

[mancow]

Actually, the term is used to mean variable split band inversion as well.

Hi again,

I think you guys are missing the point which is "rolling code" simply means the system uses a code key randomly selected (rolling) at intervals rather than one that is fixed throughout the transmission. Which type of baseband scrambling is used is irreverent when we're talking about code keys.

 

[kb2vxa]

Joseph, you WERE listening to it the other day, just ahead of the storm front there was tropo and I haven't heard it since. (;->) Keep listening to SPEN with SCQ, when the band opens you'll hear lots of interesting stuff, that's one of the reasons I don't use PL on seldom used local and regional frequencies.

Man or cow, didn't I just say that? (;->)

 

[Joseph11]

Yup. Since SPEN 2 is a national frequency, it's best to monitor it in CSQ. The only SPEN frequency I monitor with a PL is SPEN 3.

 

[RayAir]

I have no idea what that is. About 1 year ago an engineer at Transcrypt sent me a file that sounded like that same scrambler and he had no idea what it was. It must be some kind of pseudo -digital hybrid scrambler. Those are some rapid fire sync bursts! Wonder who makes it?

 

[DaveNF2G]

Just as a policy point, nobody should be using encryption routinely on interop channels. It defeats the purpose of having them.

 

[kb2vxa]

Hi again Dave and all,

I tend to agree BUT you'll find mystery signals all over the place where they shouldn't be. In this case it's a casual conversation for very long periods like a couple of hams on 2M. Once in a while I hear similar conversations in encrypted P25 locking up the scanner on a railroad frequency. Using a much narrower receiver I found the actual transmissions on a four digit "splinter" channel between two regular assignments. No such animal exists so they're unlicensed. Then there are fishing boats on railroad assignments, I could go on forever with Terry And The Pirates.

For the kids, that was a comic strip in the Sunday paper before you were born. (;->)