On Wed, 12 Mar 2003, Mike Rosing wrote:I think you're over reacting. RFID tags only have a range of centimeters.
You'd need a huge current to power them from more than 1 meter, and that's
just not going to be out on a beach in a hidden way.
I heard these ones have range up to 1.5 meters. And you need much less power if you use a directional antenna (which can be part of some fixed installation).
Since the coupling is magnetic a Faraday cage won't work. But a thin piece of mu metal would work pretty well.
Wasn't aware about RF tags being magnetically coupled. Anyone other to support/deny this?
It's bullshit. 13 MHz is undeniably RF. Yes, magnetic fields are part of the electromagnetic field.
Hadn't knew about mu metal. Thanks. :) Could be a nice thing for EM shielding, especially of things like transformers.
Don't go jumping into the abyss without some knowledge.
(ObCredentials: I worked inside a double-walled Faraday cage in 1972-73 doing Josephson junction experiments with superconducting quantum-interferometric devices, aka SQUIDs. I did a lot of shaping and bending of mu metal. I also later worked near Faraday cages and had occasion to do more experiments in them.)
Besides, EU plans to embed RF tags into paper money.
Various lengths of metallic conductors are already inside various banknotes. This is NOT the same technology as RFID. I don't disagree about it being a concern, and an area for study and experiment, but be careful not to leap to conclusions about banknotes being a location finder.
Regarding TEMPEST shielding - there is another, complementary approach for
shielding: jamming. There are vendors selling devices that drown the RF
emissions of computer equipment in noise, so TEMPEST receivers get
nothing. Are there any publicly available specs of such generators, or
even building plans?
Jamming is grossly less efficient than detection. If you want an explanation, let me know and I'll spend 10 minutes writing a small piece on it. But first, think deeply about why this is so. Think especially about recovering signals from noise.
--Tim May
"The State is the great fiction by which everyone seeks to live at the expense of everyone else." --Frederic Bastiat
