No, I suspect power companies cannot generally shut off your power from their end. There's not a separate cable from the power plant to each individual home. There are really big cables that go most of the way from the power plant, then at each neighbhorhood or block they split off into smaller cables for individual homes. That's where the meter for each home is installed, and that's where the power company can turn off your electricity.
Traditionally they sent a technician out to read each meter and turn off the electricity if necessary, but there are newer "smart meters" that communicate your usage to the power company (although I'm not sure if those can also be remotely triggered to turn off your power, I would suspect not).
Where I grew up in a small town in the Midwestern US in the 1990s, the meters were usually installed on an external wall at the back of the house. My part of town had underground power lines (good during thunderstorms, bad during road/building construction) and I suspect the meter was right where the buried cable came into the house. Every month a uniformed person from the power company would walk through everyone's backyards taking the reading from each meter.
Fun fact: most utilities and similar services have historically worked this way. I think the cable television company would just send someone to the cable box on the back of your house and flip switches to enable the channels you were paying for. There was always some kid who claimed to get HBO for free because his older cousin worked for the cable company.
Now that I think about it, I recently got a car that's new enough to have Sirius XM satellite radio built in, and I've been wondering how their access control works. Surely the satellite doesn't beam down everyone's subscription status and make their receiver hardware respect that, right? Is my car using the built-in cell phone to check whether I'm subscribed to the satellite radio? Either way, where are the bootlegged satellite radio receivers?
On the last thing, AIUI from some research (confirmed as plausible by experience with similar systems):
- The stream channels themselves are encrypted or scrambled in a way that is hard to unwind unless you have the keys (keeping non-SiriusXM radios from working)
- Each radio has two important pieces of information: a decryption key from SiriusXM and a UUID (I'd guess 64bit, as that's a pretty standard size for hardware-baked-in UUIDs. It might be 128bit instead). You can look up the UUID for your radio. Both of those things, by the way, are bog-standard now in consumer embedded systems exactly because they help prevent bootlegging.
- Channel 0 is an ID channel that constantly streams out a list of valid UUIDs and other configuration data. An un-activated radio can only tune that channel. When it sees its own ID, it enables the rest of the channels.
Quick sanity check: Assuming they have 40 million subscribers and can pass UUIDs at roughly audio rate (to make the math easy, 16-bit, 50kHz), that makes it about an hour to sync all the users. That can probably be watched by your radio in the background, so it's only an issue for initial activation.
This may be the way SirusXM works, but it is far from optimal. The best scheme is to give the radios simple sequential (or near sequential) id's, and have the station transmit a bitmap of which id's are enabled/disabled. Then it's one bit per subscriber, and can be transmitted in a few seconds. That bitmap is authenticated by a public key stored in the radio. You might want to run length encode the bitmap if you assume that in 30 years there might still be a handful of ancient radios still alive you wish to service.
Satellite bandwidth is expensive... Activation time is annoying for customers... The above scheme saves either (or both).
Just a random thought regarding activation: they could also have a channel broadcasting all new activations, so that you could put your radio into an activation mode while you're finalizing your subscription. Or they could give you an activation code that you could enter manually somehow (it could just be a simple message signed with Sirius' private key).
Yeah, TBH I just assumed it was a unique ID baked into hardware because sequential IDs are a pain to manage, but your idea would be more efficient in the base case. As far as I can tell they also transmit things like channel-specific activations, but the sequential concept still works if that is a bitmap.
Yeah, they definitely must do decryption on the device, which means they must have some tamper-proof chip that has never been broken (as far as I can tell, there's no leaked decryption key). That's actually pretty surprising to me.
Well, now I've got to get a radio and have a look.
Looking at teardowns of the current Onyx radio [0], the NXP LPC4078FET180 has both a unique ID and some mechanisms to make it very difficult to read the programmed code externally. One option would be to store the key there, and use that mcu to run all the audio decryption, processing, device activation, and protocol updates (under the control of the TMX570 running the UI etc).
The same equipment would be required regardless of what end it's on. The pole transformer feeding your house and your neighbor's house is basically passive AFAIK; it's not remotely controllable.
They could if every house had a dedicated wire to the generator and there was a massive bank of switches in a giant building next to the generator that controlled power to every house. But no grid on Earth works that way.
Traditionally they sent a technician out to read each meter and turn off the electricity if necessary, but there are newer "smart meters" that communicate your usage to the power company (although I'm not sure if those can also be remotely triggered to turn off your power, I would suspect not).
Where I grew up in a small town in the Midwestern US in the 1990s, the meters were usually installed on an external wall at the back of the house. My part of town had underground power lines (good during thunderstorms, bad during road/building construction) and I suspect the meter was right where the buried cable came into the house. Every month a uniformed person from the power company would walk through everyone's backyards taking the reading from each meter.
Fun fact: most utilities and similar services have historically worked this way. I think the cable television company would just send someone to the cable box on the back of your house and flip switches to enable the channels you were paying for. There was always some kid who claimed to get HBO for free because his older cousin worked for the cable company.
Now that I think about it, I recently got a car that's new enough to have Sirius XM satellite radio built in, and I've been wondering how their access control works. Surely the satellite doesn't beam down everyone's subscription status and make their receiver hardware respect that, right? Is my car using the built-in cell phone to check whether I'm subscribed to the satellite radio? Either way, where are the bootlegged satellite radio receivers?