[RFI] Blocking RFID Signals?

kd4e kd4e at verizon.net
Wed Dec 28 23:10:42 EST 2005


On another list we have a discussion going as to how
one might block/eliminate unwanted RFID communications.

They are adding RFID tags, some active, some passive,
to a wide varity of things including clothes, electronics,
drivers licenses, credit cards, etc.

EPasses for toll roads are not only being read to pay
tolls but to also count vehicles on non-toll roads.

Many Hams, and non-Hams, are concerned about invasion
of privacy issues.

One person simply cut the tiny RFID device out of his
new American Express card.  He has yet to try to use
it to discover if it will be rejected (it is separate
from the magnetic strip).

Another keeps his EPass at home unless he intends to
be on the toll road.

I have been told that the new FL drivers licenses will
contain RFID tags.

Starting with the proposal that there is no contract,
law, or regulation that prevents the removal of these
little "demons" I have offered them several ideas as
to how they might be disabled.  I would like to heard
from the more informed folks on this list.

I am also curious as to what container might be necessary
to block the signals.  Someone said that the freqs vary
widely from HF up into UHF.

No paranoia ... yet!  ;-)  At the moment just a healthy
Ham curiosity as to how one might manage the RF!

I am guessing that the same frequency transmitted in
close proximity at a significant power level should
fry the circuit without harm to the mag strip.

Another option might be one of those cold soldering
irons, though it may leave an obvious burn mark -
you could try two pinhole contacts where you see leads
to the IC so as to momentarily apply the juice across
its circuitry.

A third option might be a little spot applied liquid
nitrogen like they use to remove warts and other small
growths.  Freeze the circuit area, then give it a sharp
rap, might just cause it to short out internally ...
don't know if the credit card plastic could handle
the stress.

A fourth option might be to apply some metallic paint
such as used to rf-seal containers.  If applied to
each side and perhaps a few pinholes so it connects
on both sides may create a thin yet effective rf
shield around the RFID chip.

WDYT?

doc

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