Can Faraday Cages Tame Wi-Fi? 145
mrraven writes "An article at TechWorld discusses the increased need for wireless network security. One possible solution to this problem is the use of building-wide Faraday cages to block the wireless signal from 'leaking'." From the article: "Small installations of RF shielding don't have to be expensive, and the basic concept of a Faraday cage can be extended to all kinds of small everyday objects. Leather wallets sandwiched with a conductive RF-shielding layer can prevent RFID scanners from reading personal information implanted in everything from RFID-enabled access control cards to some credit cards; they're widely available for as little as US$15. For those favoring a more DIY route, several Web sites have information on how to make an RFID-blocking wallet with duct tape and aluminum foil."
Faraday Cages will work (Score:5, Informative)
Re:What about windows? (Score:5, Informative)
Brett
Have you ever actually used a Faraday cage? (Score:5, Informative)
Real Faraday cages are an unmitigated pain to deal with. The ones used for RF testing typically have a heavy door, like a walk-in refrigerator, with conductive fingers all around the doorframe that seal against the door. It's not enough to have metal; all the metal has to be connected. And slots will pass a wavelength up to the length of the slot.
The ones used for high-security classified work are even worse. They're made of welded metal panels. They're a few feet off the ground, so the underside can be checked. Any I/O is fibre optic. Power goes in through huge low-pass filters. Air goes through metal mesh filters. Double doors work like an airlock, and there's a compressed-air system to force the RF-tight door seals. Periodic testing (transmitter inside, receiver outside) insures the tank is really RF-tight.
Not a fun work environment.
Painting the walls with conductive paint is a joke.
There's nothing mysterious about any of this. RF propagation is well understood, and the test gear is easy to obtain. Ask any ham.
Re:The truth may be out there... (Score:5, Informative)
No, but it will keep the voices from using your neighbor's access point.
Re:Solves the wrong problem (Score:3, Informative)
Re:Faraday Cages will work (Score:5, Informative)
HOWTO: protect your wireless network (Score:1, Informative)
(b) declare an ipsec tunnel from your laptop to your gateway.
(c) set ipsec policy to require it for all traffic.
(d) rtfm
ip link set dev wireless arp off up
ip address add dev wireless local 192.168.1.2 peer 192.168.1.3
ip neighbor add dev wireless to 192.168.1.3 lladdr 00:11:24:2c:38:c6 nud permanent
setkey -c >/dev/null <<-END
flush;
spdflush;
add 192.168.1.2 192.168.1.3 esp 256 -m tunnel
-E aes-cbc 0x25d8d1bbcf9b7b416ebd7ce514627539f12dc64e3e75c5a
-A hmac-sha1 0x17f98a8f668324191ee406855e81130fb17f7726;
add 192.168.1.3 192.168.1.2 esp 512 -m tunnel
-E aes-cbc 0x25d8d1bbcf9b7b416ebd7ce514627539f12dc64e3e75c5a
-A hmac-sha1 0x17f98a8f668324191ee406855e81130fb17f7726;
spdadd 192.168.1.3 0.0.0.0/0 any -P in ipsec
esp/tunnel/192.168.1.3-192.168.1.2/require;
spdadd 0.0.0.0/0 192.168.1.3 any -P out ipsec
esp/tunnel/192.168.1.2-192.168.1.3/require;
END
Re:Faraday Cages will work (Score:2, Informative)
It's all about the wavelengths. If you want to block ALL EM, then yeah, you need a solid metal enclosure. But, just like you can see into your microwave oven through a wire mesh, you could also put windows on your faraday cage as long as they were covered by an appropriate wire mesh.
IIRC, the 2.5GHz of a microwave oven beam and the 2.4GHz of WiFi are both around 12 cm wavelength. The holes in the mesh on your microwave are so small that the microwaves can't make it through it without severe attenuation.
--JoeCan you hear me now? (Score:4, Informative)
Direct experience... (Score:1, Informative)
You must remember - people still have to breathe, so air must go in and out easily and in volume.
I was not directly involved in the installation (I was a user of the library), but IIRC they always had trouble getting it to not leak in some way. Think of RF as high pressure steam - it will always find a leak. Not all RF can be shielded the same way, or the one way that does work is most expensive and hardest.
I'm sure it can be made to work, if designed into the building from the start, but it's very difficult to add later.
WiFi is highly likely to be subjected to a lot of industry brainwork figuring out how to sniff it out thru Faraday cages that are supposedly "secure". I suspect a lotta snake oil could be sold this way.
Re:What about windows? (Score:3, Informative)