[Novalug] Mythbusters, RFID

Keith Howell keith.c.howell@gmail.com
Fri May 4 20:39:35 EDT 2012


On 05/04/2012 04:51 PM, Bonnie Dalzell wrote:
> On Fri, 4 May 2012, William Sutton wrote:
> 
>> Would a very strong magnet do the trick?  :-)
>>
>> William Sutton
>>
> 
> According to this essay the magnet powers the  RFID chip, allowing it to
> broadcast.

In simple terms, it is RF induction, not just a magnet.

The changing magnetic field of the receiver induces a small current into
the antenna coil of the RFID chip. This charges up a small capacitor
that powers the CPU of the chip. The firmware in the chip then alters
the inductance of the antenna which causes the transmitting antenna to
alter, which in turn can be detected by the circuit in the reader.

There are several ways to destroy the RFID chip. The easiest is to put
it near one of the counters in Home Depot or Best Buy when you wave one
of their items across it. The "doing" that you hear is a large
electromagnetic pulse that melts the RFID chip in the anti-shoplifting tag.

You can also build your own out of a disposable flash camera. Remove the
flash tube and replace it with several turns of heavy copper wire.
Charge the flash unit. Place the coil near your card and then hit the
shutter button.

The problem with all of these methods is that you stand the strong
chance of destroying the magstripe information as well. Also, don't put
your fancy car key anywhere near these methods as it will stop that
working as well!!

The final way is to use a *very* strong light source and shine it
through the card. This will allow you to see the location of the chip
inside the plastic. Then mark the card where the chip is located and
finally drive a small sharp object through it. You will need to test if
you hit the chip, but this method is not normally detectable by cashiers
and they don't complain. If you use the hole-punch method, they tend to
complain about damaged cards.

-- 
Keith



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