On Thu, 31 Mar 2005, Major Variola (ret) wrote: > At 10:08 PM 3/31/05 +0200, Eugen Leitl wrote: > > government plan to insert remotely readable chips in American > > passports, calling the chips [2]homing devices for high-tech > > muggers, > > So the market for faraday-cages for your passport will grow to > equilibrium. A cage will cost less than a buck in parts, easily > affordable by the clueful. The damage to the clueless will > quickly be the best advertising for the product. Since we > have been wearing conductive mesh burkhas for some time, > the only inconvenience will be for the terahertz voyeurs > employed by the TSA.
Beware of one gotcha. Faraday cage will shield only the electrical component. Low-frequency tags (125 kHz, typically) are magnetically coupled. Experiments shown that such tag is readable, even if entirely wrapped in aluminum foil. Laying a tag on top of a feromagnetic surface (iron sheet) does not help (probably only diminishes the range, didn't do the exact measurements yet); the sheet has to be between the tag's coil and the reader coil to be effective. Putting the tag into an enclosure made of a feromagnetic material helps, though. Altoids can proved to be a pretty effective shielding.