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Most of our local departments use encrypted radios. "Over the past few years, an increasing number of municipalities and police departments, including the Dist

Most of our local departments use encrypted radios. "Over the past few years, an increasing number of municipalities and police departments, including the District’s, have begun encrypting their radioed communications.."[1.] https://www.washingtonpost.com/local/social-issues/last-of-the-scanners-are-police-security-measures-killing-an-american-obsession/2018/12/28/4e344a62-09f5-11e9-a3f0-71c95106d96a_story.html https://www.washingtonpost.com/local/social-issues/last-of-t...

AlexandrB 6y ago
I don't think this is a positive development. It's already too easy to blackhole information that could be used to hold police accountable (body cams, arrest reports, etc.). This removes yet another avenue for citizens/journalists.
- sneak 6y ago
  The people who set the laws around radio communication regulation, those who implement that regulation, as well as the people who set police policy and budgets, prefer it that way, as they are part of the ownership class that the police actually do protect (and not the ones they murder or oppress indiscriminately). To them, the general public having visibility into the things done by the police or the military in their name is a bad thing, and the public’s money should be spent on systems to conceal those activities from public view. Transparency is something to be avoided, in the view of secrecy-heavy, military-inspired DHS (which is the driver, both policy and funding, behind much of the local domestic COMSEC upgrades). If you want it to change, you need to bark up a different tree.
dmkolobov 6y ago
Completely outside of my area of expertise, so this may be a silly question, but are police transmissions distinguishable from others in their encrypted form? If so, there could still be a use case for knowing _where_ the cops are. Wonder if some sort of mesh could be used to triangulate the positions of these signals.
- alvern 6y ago
  I think the repeaters would block out any of the mobile radios. So you could see the dispatchers easily, but the individual mobile operators (EMS, Fire, Police) would be hard to distinguish. If the mesh was every Digital TV tuner inside a municipality, then maybe the mesh could triangulate position.
- oasisbob 6y ago
  You could look for the repeater uplink, maybe. Keep in mind that these public radio systems are often used by firefighters and other agencies. Finding police specifically would probably involve some sort of metadata leak in the radio signaling protocols.
- ryanlol 6y ago
  Often they are, yes. It’s relatively easy to use an USRP to generate alerts when someone is using TETRA nearby. But sure, other agencies may generate false positivies.
- deleted 6y ago
  [deleted]
- Simulacra 6y ago
  Outside of my area as well, but, IIRC Kevin Mitnick wrote about using a radio set to encrypted frequencies. When he was out and about, if he heard traffic on those frequencies, then he knew the FBI etc. must be nearby.
catalogia 6y ago
What I heard is many police departments now encrypt their radio communications, with the exception of dispatch which they keep in the clear as a concession to the media and ambulance chasers.
- themodelplumber 6y ago
  They also refer each other to their MDT or cell when working, which is equally effective at cutting out the public (whether intended or no). In many rural areas, analog FM voice is still in use with no encryption, which I've heard is at least sometimes due to more favorable propagation characteristics for reception at a distance.
  - hajile 6y ago
    Digital signal is clearer, but all or nothing. I know a fire chief who told me that some stations have switched back to analog. Some firefighters allegedly went silent and their bodies were found later. I guess it's believed that they attempted to radio for help, but the "digital cliff" stopped anything at all from getting through. If they'd heard someone calling for help, they could have gone there -- even if they didn't know exactly what the issue was. I'm sure pricing is a factor in a lot of areas. $150 will buy a decent analog radio. The same thing, but digital will cost $300-500. Cheap Chinese radios can be had for as low as $30 or so. With just 100 radios saving $200 each, you get 20k to spend on other things. That matters a lot to rural police and even more to EMS (especially volunteer groups).
cwkoss 6y ago
Does anyone have information about how frequently keys are rotated or exchanged? Seems like keeping 100 radios on the same channel could be hard to do without the potential for human error to leak some data - cops aren't typically very tech savvy.
- sneak 6y ago
  The radios are re-keyed periodically over the air, or at least they can be. Not sure how often it happens in practice. There’s also a capability, mandated by the federal interoperability standards (compliance with which federal free money to upgrade local PD radios hinges upon) to zeroize (erase/disable) encryption keys in a radio remotely, for example if one is lost or stolen, to prevent rogue network access. Misuse of the rekeying admin keys to remotely disable police radios in bulk is a very interesting DoS, and one that should be noted well by (usually civilian outsourced) police radio maintenance admins presently reading this comment if cops or other users of these encrypted radio systems start being deployed to mass murder civilians. As I understand it, the same interoperability protocols also can interrogate the radios for their locations if GPS equipped. (I have not personally read the spec docs yet.) I’d love to see the mashup made of that data, or an oversight organization using it to track criminal cops and parallel construction efforts.

AlexandrB 6y ago

I don't think this is a positive development. It's already too easy to blackhole information that could be used to hold police accountable (body cams, arrest reports, etc.). This removes yet another avenue for citizens/journalists.

sneak 6y ago
The people who set the laws around radio communication regulation, those who implement that regulation, as well as the people who set police policy and budgets, prefer it that way, as they are part of the ownership class that the police actually do protect (and not the ones they murder or oppress indiscriminately). To them, the general public having visibility into the things done by the police or the military in their name is a bad thing, and the public’s money should be spent on systems to conceal those activities from public view. Transparency is something to be avoided, in the view of secrecy-heavy, military-inspired DHS (which is the driver, both policy and funding, behind much of the local domestic COMSEC upgrades). If you want it to change, you need to bark up a different tree.

dmkolobov 6y ago

Completely outside of my area of expertise, so this may be a silly question, but are police transmissions distinguishable from others in their encrypted form? If so, there could still be a use case for knowing _where_ the cops are. Wonder if some sort of mesh could be used to triangulate the positions of these signals.

alvern 6y ago
I think the repeaters would block out any of the mobile radios. So you could see the dispatchers easily, but the individual mobile operators (EMS, Fire, Police) would be hard to distinguish. If the mesh was every Digital TV tuner inside a municipality, then maybe the mesh could triangulate position.
oasisbob 6y ago
You could look for the repeater uplink, maybe. Keep in mind that these public radio systems are often used by firefighters and other agencies. Finding police specifically would probably involve some sort of metadata leak in the radio signaling protocols.
ryanlol 6y ago
Often they are, yes. It’s relatively easy to use an USRP to generate alerts when someone is using TETRA nearby. But sure, other agencies may generate false positivies.
deleted 6y ago
[deleted]
Simulacra 6y ago
Outside of my area as well, but, IIRC Kevin Mitnick wrote about using a radio set to encrypted frequencies. When he was out and about, if he heard traffic on those frequencies, then he knew the FBI etc. must be nearby.

catalogia 6y ago

What I heard is many police departments now encrypt their radio communications, with the exception of dispatch which they keep in the clear as a concession to the media and ambulance chasers.

themodelplumber 6y ago
They also refer each other to their MDT or cell when working, which is equally effective at cutting out the public (whether intended or no). In many rural areas, analog FM voice is still in use with no encryption, which I've heard is at least sometimes due to more favorable propagation characteristics for reception at a distance.
- hajile 6y ago
  Digital signal is clearer, but all or nothing. I know a fire chief who told me that some stations have switched back to analog. Some firefighters allegedly went silent and their bodies were found later. I guess it's believed that they attempted to radio for help, but the "digital cliff" stopped anything at all from getting through. If they'd heard someone calling for help, they could have gone there -- even if they didn't know exactly what the issue was. I'm sure pricing is a factor in a lot of areas. $150 will buy a decent analog radio. The same thing, but digital will cost $300-500. Cheap Chinese radios can be had for as low as $30 or so. With just 100 radios saving $200 each, you get 20k to spend on other things. That matters a lot to rural police and even more to EMS (especially volunteer groups).

cwkoss 6y ago

Does anyone have information about how frequently keys are rotated or exchanged? Seems like keeping 100 radios on the same channel could be hard to do without the potential for human error to leak some data - cops aren't typically very tech savvy.

sneak 6y ago
The radios are re-keyed periodically over the air, or at least they can be. Not sure how often it happens in practice. There’s also a capability, mandated by the federal interoperability standards (compliance with which federal free money to upgrade local PD radios hinges upon) to zeroize (erase/disable) encryption keys in a radio remotely, for example if one is lost or stolen, to prevent rogue network access. Misuse of the rekeying admin keys to remotely disable police radios in bulk is a very interesting DoS, and one that should be noted well by (usually civilian outsourced) police radio maintenance admins presently reading this comment if cops or other users of these encrypted radio systems start being deployed to mass murder civilians. As I understand it, the same interoperability protocols also can interrogate the radios for their locations if GPS equipped. (I have not personally read the spec docs yet.) I’d love to see the mashup made of that data, or an oversight organization using it to track criminal cops and parallel construction efforts.