"R. A. Hettinga" <[EMAIL PROTECTED]> writes:At 12:35 PM -0400 5/27/04, John Kelsey wrote:Does anyone know whether the low-power nature of wireless LANs protects them from eavesdropping by satellite?
It seems to me that you'd need a pretty big dish in orbit to get that kind of resolution.
The Keyholes(?) are for microwaves, right?
Dunno if it would work in orbit,, but you can get surprising results right here on earth using phased arrays.
Vivato is selling very long range phased array equipment as long range/high quality 802.11 basestations, but you could do precisely the same trick to eavesdrop instead of to communicate. With enough computing power, one device could listen in on every 802.11 communication in a very large radius.
I don't know how practical it would be to set up some sort of large scale phased array in orbit -- I suspect the answer is "not practical at all" -- but the principle could apply there, too.
I would say quite practical. A huge advantage for the attacker is that 802.11b/g is in a fixed frequency band. A half-wave dipole is 6.25 cm long. A large phased array could be assembled out of printed circuit board tiles, each with many antennas.
The outdoor range for 802.11 is up to 100 m. Low earth orbit is about 150 km. That is a factor of 1500. Power attenuation is the square of that, which works out to a 64 db loss. Throw in another 10 db for slant range, building attenuation, etc. The loss has to be made up by a combination of antenna gain, improved receiver performance and better signal processing. That doesn't sound undoable.
A single LEO satellite would only have a few minutes of visibility per day over any one location on Earth. That suggests an active attack, where the satellite looks for files or even changes data. The satellite's ability to transmit at much higher power levels is an advantage.
A third option is spot jamming. Here high power means one can get away with a smaller antenna, perhaps wrapped around a cheaper spin stabilized satellite. Such a system could be used to briefly disable 802.11-based security systems, perhaps allowing a spy to gain access to a building.
Other interesting possibilities include long endurance remotely-piloted aircraft, balloons and small receiving stations that could be planted by spies or even parachuted into position. I'm sure 802.11 has given the SIGINT community much joy.
Arnold Reinhold
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