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Can Faraday Cages Tame Wi-Fi?

Posted by ryuzaki0 on from the heeya-heeya-back-wifi-back dept.

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."

9 of 145 comments (clear)

  1. Faraday Cages will work by jmauro · · Score: 5, Informative

    Only if you don't want cell phone coverage or look out side. I work in a building that is EM sheilded using a Faraday cage. It was designed to test new radios so you didn't want outside signals coming in to mess up the test. Needless to say a all-metal no windowless office sucks. You have to go out side to make a cell call and when the AC breaks you're screwed because the place turns into an oven with no windows to open. It's a nice idea, but I doubt most wouldn't like to work in such a place 24-7. I sure don't.

    1. Re:Faraday Cages will work by JesseL · · Score: 5, Informative

      A wire screen tends to block EM with a wavlength greater than about twice the size of the holes in the mesh. Since the visible spectrum is in the few hundred nanometer range, and most RF communication happens at wavelengths over 5 centimeters, a screen is a very viable option.

      --
      "Prefiero morir de pie que vivir siempre arrodillado!"
    2. Re:Faraday Cages will work by Mr+Z · · 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.

      --Joe
      --
      Program Intellivision!
  2. Re:What about windows? by Brett+Buck · · Score: 4, Informative

    Window shielding is a well-established technology. Note http://www.lessemf.com/plastic.html. This has been done for decades for secure facilities. There's nothing new about RF shielded/Faraday cage buildings.

                Brett

  3. Have you ever actually used a Faraday cage? by Animats · · Score: 4, 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.

  4. Re:The truth may be out there... by Dachannien · · Score: 4, Informative

    Will it stop the voices as well?

    No, but it will keep the voices from using your neighbor's access point.

  5. Re:Solves the wrong problem by Bishop · · Score: 2, Informative

    A complete faraday cage will contain RF EM waves for the same reason that it will keep EM out.

  6. Can you hear me now? by Spazmania · · Score: 3, Informative

    "Can you hear me now?" No, in fact it will stop your cell phone reception too.

    --
    Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
  7. Re:What about windows? by JesseL · · Score: 2, Informative

    A faraday cage does not need to be conected to an earth ground. In fact a lot of electronic equipment uses the cage/shield its self as a "ground".

    --
    "Prefiero morir de pie que vivir siempre arrodillado!"