Encryption? Why does it work like this?

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mrova

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I notice that when my scanner is stopped on some of the police channels that are encrypted (sometimes), that one side of the conversation is understandable and clear, but when the other person replies, it's encrypted. The line of conversation can go on and on, one side is clear, the other side is encrypted. I understand why encryption might be important, but I don't understand why "half" of the conversation is encrypted. Follow up question - Just how do they do that? Is there a button the one person holds while speaking?
The one-sided encryption doesn't happen all the time on the particular channel, just now and then, when they're needing to be a bit covert.
SV
 

mancow

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If a radio is equipped with a proper key it will automatically detect the encrypted traffic and decode it. With the old analog securenet it's pretty obvious to the users when one goes encrypted because the voice quality is significantly degraded. With the new P25 digital systems the encrypted and non encrypted voice quality is exactly the same. If one party forgets to flip the switch and nobody is watching the display indicators then they may never realize that one is not in secure mode.
 

Patch42

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I heard something similar a few weeks ago. It was clearly a group on a stakeout keeping in touch over the radio. There must have been at least five separate units involved. All were in the clear except one.

I assume it's because the radios are accidentally configured differently. I can't believe it's being done on purpose.
 

zz0468

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Sounds like a case of the radio's capability exceeding the user's training.
 

JnglMassiv

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I assume it's because the radios are accidentally configured differently. I can't believe it's being done on purpose.
Right, it's not intentional. The radios are all keyed alike and the ones with the code switch off are monitorable. The audio quality issue may not be apparent to your average UC.
 

Grog

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The OP has been expertely answered, but I'll add this...

Back in the mid-late 90s I monitored the NC state marine fisheries officers a lot, and there were times I would hear them talking to the dispatcher encrypted, but the dispatcher was always in the clear.

I would take a guess and say that might be in case a radio lost a key so they would always be able to hear the dispatcher.
 

mrova

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thanks

the answers make sense. Didn't think about their possibly not having flipped the switch and not realized. And, at this point, I haven't heard a single conversation where both parties were encrypted. thanks for the insight.
sv
 

iMONITOR

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I would think a radio would automatically switch to encrypted mode for transmit when responding a TG that was encrypted. It might also be a good idea to have the radio with encryption enabled, give some indication that the radio(s) responding did, or did not have encryption enabled.
 

JnglMassiv

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I would think a radio would automatically switch to encrypted mode for transmit when responding a TG that was encrypted. It might also be a good idea to have the radio with encryption enabled, give some indication that the radio(s) responding did, or did not have encryption enabled.
There are some options (at least for Motorola). Trunked radios/systems might have some more clever idiot-proofing features that I'm unfamiliar with, too.

You can program the radios to give a tone on key-up if the radio is uncoded. Now, it's up to your operators to listen for that tone and know what it means.

You can also program your radio so that it doesn't pass clear audio unless you have your switch properly selected. This could be bad if one of your guys is goofing around, takes his battery off, loses the key and gets into trouble. His calls for help would go unheard.

I think there's another indicator that an incoming tx is encoded, too. Maybe an LED lights or something.

mrova said:
And, at this point, I haven't heard a single conversation where both parties were encrypted. thanks for the insight.
That's pretty lucky. In my experience, it's one or two team members who forget to encode and you only hear a very small portion of the traffic. Still, this is pretty uncommon. Around here, I typically encounter encryption during surveillance and other smaller team operations. In other words, no dispatcher is involved.

I've heard short range, simplex surveillance with a helicopter involved. They had it completely backwards: the guys on the ground were coded but the heli was clear. The guy with the high power radio and an antenna a mile up was transmitting positions and target headings for all of Chicagoland to hear.
 

RKG

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There are some options (at least for Motorola). Trunked radios/systems might have some more clever idiot-proofing features that I'm unfamiliar with, too.

You can program the radios to give a tone on key-up if the radio is uncoded. Now, it's up to your operators to listen for that tone and know what it means.

You can also program your radio so that it doesn't pass clear audio unless you have your switch properly selected. This could be bad if one of your guys is goofing around, takes his battery off, loses the key and gets into trouble. His calls for help would go unheard.

I think there's another indicator that an incoming tx is encoded, too. Maybe an LED lights or something.

That's pretty lucky. In my experience, it's one or two team members who forget to encode and you only hear a very small portion of the traffic. Still, this is pretty uncommon. Around here, I typically encounter encryption during surveillance and other smaller team operations. In other words, no dispatcher is involved.

I've heard short range, simplex surveillance with a helicopter involved. They had it completely backwards: the guys on the ground were coded but the heli was clear. The guy with the high power radio and an antenna a mile up was transmitting positions and target headings for all of Chicagoland to hear.

As noted, others have explained the technical side of the observed phenomenon. However, I'll add that this shows some lack of insight (or implementation) by the system designer.

We've largely eliminated this issue by treating the encrypted and clear as separate channels, invoked by the channel selector.
 

adwcbw

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I notice that when my scanner is stopped on some of the police channels that are encrypted (sometimes), that one side of the conversation is understandable and clear, but when the other person replies, it's encrypted. The line of conversation can go on and on, one side is clear, the other side is encrypted. I understand why encryption might be important, but I don't understand why "half" of the conversation is encrypted. Follow up question - Just how do they do that? Is there a button the one person holds while speaking?
The one-sided encryption doesn't happen all the time on the particular channel, just now and then, when they're needing to be a bit covert.
SV
I am guessing that you are listening to Chesterfield covert guys, there appears to be one guy who turned on encryption a year or two ago and he never turned it off. A friend who is a ex-officer told me that there is a code to punch in to turn encryption on or off. I have also heard Chesterfield ask officers that have encryption turned on if they know it is turned on.

Andy
 

davidbond21

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Huh, glad I stumbled across this because I was getting ready to start a thread asking a very similar question. My question involved DEA mobile surveillance, using analog voice. I could hear the lead vehicle from 12 miles away, calling out the moves of the principal as they followed him all around the city, but not the secondary vehicles that shouldn't have been far behind.

I can't believe the explanation for this phenomenon could be so simple as the operator not engaging the encryption, not that I'm complaining(although you'd think you'd expect better from a federal officer). Their mistake is my listening pleasure.
 

mrova

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adwcbw

You are right - I'm listening to the Chesterfield covert guys. I figured they have some way of controlling encryption and that the one guy that isn't didn't have information that was as important as the other guy, and when it was getting pretty serious as to specific location of a target, etc., then the one guy would just go encrypted.
I heard the communications when Obama came into town, that was regular police channel and not encrypted, which surprised me...just "coded messages." Do the regular police channels have the capability to encrypt or is that just specific to the individual radio?
sv
 

LEH

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There may be a number of variables to this.

York County Virginia shared TRS system is that way too. I have yet to figure out any relationship to the encryption and unencrypted transmissions.

Sometimes it is the dispatcher encrypted and the mobile unit in the clear, other times it is reversed. Sometimes, it even seems that both are in the clear. Like some kind of system random encryption generator.

Now there are three systems that seem to be fully encrypted on this system. The private security for Williamsburg's Kings Mill subdivision, William and Mary Police, and Poquoson PD (though I do hear the occasional clear dispatch, most is encrypted). So there must be some way to for the system to set everyone on (or the training is better for these users).

The rest of the talk groups for York County (fire, sheriff, schools, maintenance are hit and miss) as are Williamsburg City and James City County talk groups.

One of my neighbors down the street is an EMS supervisor for the YCFD and he told (as he was parked in front of my house watching a broken gas line incident) that they could turn encryption on and off with their (or at least his) particular radios.

I wish there were a really good simple answer to this, but there doesn't seem to be.
 

wlmr

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There may be a number of variables to this.

(good, valid info removed for brevity)

I wish there were a really good simple answer to this, but there doesn't seem to be.
There are options in several locations that all add to the confusion.

The dispatch consoles can be set up to have a button to turn on/off encryption. They can also be set up on any console application reset/restart to have all the encryption capable talkgroups start up encrypted or clear. Or the talkgroup may be set up at the console to not be switchable at all. Another variable, how well are the dispatchers trained?

At the system level a talkgroup can be set up as switchable, clear only, or encrypted only.

In the radios out in the field, the talkgroups can be set up as clear only, encrypted only, or switchable. If they're switchable they can beep to warn the user they're transmitting without encryption or stay quiet. The switch can be programmed for the default location for the radio - or almost any other button or menu location. Again, the final confuser in this is how well are the users trained?
 
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