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What?? You mean I can't pick up my wifi from the end of the garden, but there's a chance the US government is listening in from space? Is that seriously possib

What?? You mean I can't pick up my wifi from the end of the garden, but there's a chance the US government is listening in from space? Is that seriously possible?

sitharus 9y ago
While I can’t comment on if it would be possible from orbit, there are two components to receiving a radio signal - transmitter strength and antenna gain. These work together to provide a signal clear enough to be amplified in to something usable. In a modern portable device the antenna is quite small and often close to other electronics, so the gain is not great. You can buy dedicated hardware that can receive over much greater distances. Additionally device antennas are omnidirectional, so they pick up noise from every direction but the signal from only one. A directional antenna has much greater gain as it excludes most of the noise.
- dullgiulio 9y ago
  But isn't both WiFi and LTE encrypted?
  - sitharus 9y ago
    Yes, but you can obtain other info without the keys, such as SSID locations. Personally I’m doubtful, unless the satellite was in geostationary orbit then it wouldn’t have that long over each location. I guess if it was in a Molniya-type orbit, but that would take it quite high. Guess we’ll never know.
  - patcheudor 9y ago
    It depends. Both WiFi and LTE can be attacked via evil-twin attacks where a base station pretends to be the legitimate one. https://en.wikipedia.org/wiki/Evil_twin_(wireless_networks) https://en.wikipedia.org/wiki/Evil_twin_(wireless_networks) and: https://www.documentcloud.org/documents/4392401-4G-LTE-attacks-paper.html https://www.documentcloud.org/documents/4392401-4G-LTE-attac...
  - paranoidrobot 9y ago
    Given how frequently we discover major flaws in the implementation of TLS, despite how well that is scrutinised. It's not unreasonable to believe there would similarly be major flaws in the implementation of 3G/LTE security that could be exploited.
yetihehe 9y ago
Yep, https://www.cnet.com/news/new-wi-fi-distance-record-382-kilometers/ https://www.cnet.com/news/new-wi-fi-distance-record-382-kilo... . If you have big enough antena and state of the art amplifiers, 500km is not unbelievable and that is high enough to orbit a satellite (for example ISS is at about 405km now). Plus, you have only about 100km of atmosphere (I might be wrong here).
- jacquesm 9y ago
  It's not that simple, those point-to-point links are done with both highly directional antennae at both ends. You'd need to deal with Doppler (the satellite is moving pretty quickly, and likely in a relatively complex path relative to the transmitter), attenuation because of rainfall and other atmospheric effects, polarization, non-directional transmitter antenna and the effect of likely having 1000's of transmitters of roughly the same kind in the footprint of the satellite antenna. It isn't impossible, but 'Yep' is a bit of a shortcut, and if they pull this off it would be quite the technological feat. It also would mean that if this is possible that you wouldn't need anything special to implement SpaceX's vision of ubiquitous internet using LEO satellites, the antenna tech for that is quite exotic and requires a roof mounted structure, something that almost no WiFi transmitter has. So those WiFi distance records are not at all on the same level as picking up a single WiFi signal from space, the one requires cooperation on both sides, the other has to do everything on one end (but obviously with a larger budget and some really clever people behind it). If you've ever done such a long haul WiFi link then you'll know how hard it is to line up the dishes and how easy it is to lose the connection due to wind, vibration or water in the atmosphere.
  - jjoonathan 9y ago
    They've got billions of dollars to dump into a ginormous phased array with nearly perfect acoustic isolation, no gravity or kids tripping over wires to mess up an absurdly long baseline, custom software stack, custom steering loop, and probably even custom silicon. I'd expect them to do substantially better than some dudes in the desert with glorified cookware. Especially when it comes to the steering loop, because if there's one thing phased arrays are really, really good at, that's it.
wernercd 9y ago
Not picking up wifi in garden... could be akin to "I can't see the ground clearing while in a 747... so what can they really see from orbit?" https://motherboard.vice.com/en_us/article/8qx54b/googles-satellites-could-soon-see-your-face-from-space https://motherboard.vice.com/en_us/article/8qx54b/googles-sa... Considering you can "legally" see "manholes and mailboxes" from orbit? What could we see if not "limited" by laws? Whats visible now considering that article was 2014... Grab your tin-foil hats.
dboreham 9y ago
Yes. Space isn't that far away and with a big enough antenna... Note that satellite phones and so on (tv) work like this in reverse. USG has been listening to EM signals from space (elint) since the space age began.
bsder 9y ago
Big antennas can pick up really small signals. Deep space network video where they talk about the fact that Voyager I/II is NOT the toughest signal to grab (apparently Mars Exploration Rover is due to small antennas): https://youtu.be/1rCrfQUcXDI?t=188 https://youtu.be/1rCrfQUcXDI?t=188 That being said, I doubt you could pick up WiFi and dig it out of the noise at space distances. However, you probably can relay signal intelligence from a drone or a human who is using a specific modulation known to the satellite.
jacquesm 9y ago
Not an expert. But reasonably knowledgeable about what you could do with antenna tech and while this is possible in theory if there is only one transmitter in all of the Earth-side footprint of where that antenna points I highly doubt you could recover all the signals of all the individual WiFi transmitters in that footprint which is what would be necessary to pull a single data stream out of the mess. Even so, if you're in a rural area and your next door neighbour is a mile away or so with the right antenna this might very well be possible. Keep in mind that antenna gain is the rough equivalent of increased transmitter power, so a very good antenna can offset a lack of power at the transmitter site.

What?? You mean I can't pick up my wifi from the end of the garden, but there's a chance the US government is listening in from space? Is that seriously possible?

sitharus 9y ago

While I can’t comment on if it would be possible from orbit, there are two components to receiving a radio signal - transmitter strength and antenna gain. These work together to provide a signal clear enough to be amplified in to something usable. In a modern portable device the antenna is quite small and often close to other electronics, so the gain is not great. You can buy dedicated hardware that can receive over much greater distances. Additionally device antennas are omnidirectional, so they pick up noise from every direction but the signal from only one. A directional antenna has much greater gain as it excludes most of the noise.

dullgiulio 9y ago
But isn't both WiFi and LTE encrypted?
- sitharus 9y ago
  Yes, but you can obtain other info without the keys, such as SSID locations. Personally I’m doubtful, unless the satellite was in geostationary orbit then it wouldn’t have that long over each location. I guess if it was in a Molniya-type orbit, but that would take it quite high. Guess we’ll never know.
- patcheudor 9y ago
  It depends. Both WiFi and LTE can be attacked via evil-twin attacks where a base station pretends to be the legitimate one. https://en.wikipedia.org/wiki/Evil_twin_(wireless_networks) https://en.wikipedia.org/wiki/Evil_twin_(wireless_networks) and: https://www.documentcloud.org/documents/4392401-4G-LTE-attacks-paper.html https://www.documentcloud.org/documents/4392401-4G-LTE-attac...
- paranoidrobot 9y ago
  Given how frequently we discover major flaws in the implementation of TLS, despite how well that is scrutinised. It's not unreasonable to believe there would similarly be major flaws in the implementation of 3G/LTE security that could be exploited.

yetihehe 9y ago

Yep, https://www.cnet.com/news/new-wi-fi-distance-record-382-kilometers/ https://www.cnet.com/news/new-wi-fi-distance-record-382-kilo... . If you have big enough antena and state of the art amplifiers, 500km is not unbelievable and that is high enough to orbit a satellite (for example ISS is at about 405km now). Plus, you have only about 100km of atmosphere (I might be wrong here).

jacquesm 9y ago
It's not that simple, those point-to-point links are done with both highly directional antennae at both ends. You'd need to deal with Doppler (the satellite is moving pretty quickly, and likely in a relatively complex path relative to the transmitter), attenuation because of rainfall and other atmospheric effects, polarization, non-directional transmitter antenna and the effect of likely having 1000's of transmitters of roughly the same kind in the footprint of the satellite antenna. It isn't impossible, but 'Yep' is a bit of a shortcut, and if they pull this off it would be quite the technological feat. It also would mean that if this is possible that you wouldn't need anything special to implement SpaceX's vision of ubiquitous internet using LEO satellites, the antenna tech for that is quite exotic and requires a roof mounted structure, something that almost no WiFi transmitter has. So those WiFi distance records are not at all on the same level as picking up a single WiFi signal from space, the one requires cooperation on both sides, the other has to do everything on one end (but obviously with a larger budget and some really clever people behind it). If you've ever done such a long haul WiFi link then you'll know how hard it is to line up the dishes and how easy it is to lose the connection due to wind, vibration or water in the atmosphere.
- jjoonathan 9y ago
  They've got billions of dollars to dump into a ginormous phased array with nearly perfect acoustic isolation, no gravity or kids tripping over wires to mess up an absurdly long baseline, custom software stack, custom steering loop, and probably even custom silicon. I'd expect them to do substantially better than some dudes in the desert with glorified cookware. Especially when it comes to the steering loop, because if there's one thing phased arrays are really, really good at, that's it.

wernercd 9y ago

Not picking up wifi in garden... could be akin to "I can't see the ground clearing while in a 747... so what can they really see from orbit?" https://motherboard.vice.com/en_us/article/8qx54b/googles-satellites-could-soon-see-your-face-from-space https://motherboard.vice.com/en_us/article/8qx54b/googles-sa... Considering you can "legally" see "manholes and mailboxes" from orbit? What could we see if not "limited" by laws? Whats visible now considering that article was 2014... Grab your tin-foil hats.

dboreham 9y ago

Yes. Space isn't that far away and with a big enough antenna... Note that satellite phones and so on (tv) work like this in reverse. USG has been listening to EM signals from space (elint) since the space age began.

bsder 9y ago

Big antennas can pick up really small signals. Deep space network video where they talk about the fact that Voyager I/II is NOT the toughest signal to grab (apparently Mars Exploration Rover is due to small antennas): https://youtu.be/1rCrfQUcXDI?t=188 https://youtu.be/1rCrfQUcXDI?t=188 That being said, I doubt you could pick up WiFi and dig it out of the noise at space distances. However, you probably can relay signal intelligence from a drone or a human who is using a specific modulation known to the satellite.

jacquesm 9y ago

Not an expert. But reasonably knowledgeable about what you could do with antenna tech and while this is possible in theory if there is only one transmitter in all of the Earth-side footprint of where that antenna points I highly doubt you could recover all the signals of all the individual WiFi transmitters in that footprint which is what would be necessary to pull a single data stream out of the mess. Even so, if you're in a rural area and your next door neighbour is a mile away or so with the right antenna this might very well be possible. Keep in mind that antenna gain is the rough equivalent of increased transmitter power, so a very good antenna can offset a lack of power at the transmitter site.