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RFID MasterCard
starburst writes "MasterCard introduces a
RFID MasterCard called PayPass in Orlando Florida. They tout the convenience of no more swiping or giving your card to cashiers. They claim the card has to be within an inch of the reader to be read -- how long till criminals are walking the malls, or next to you in line with portable readers getting your card information?"
How about right now?
CARD-SAFE(TM) WALLET
"Protects Credit Cards And Other Valuables From EMF Damage"
The magnetic strip on your credit card can be damaged, even erased by exposure to strong magnetic fields. Ordinary magnets will do it, but so can less obvious sources such as anti-theft scanners in department stores or libraries, small electric motors, even speaker magnets (someone told us that electromagnetic harassment can be used to erase credit cards too)! This handsome black leather wallet is discretely lined with both RF and magnetic field shielding materials and offers excellent protection. Includes 2-compartment bill fold, 6-compartment credit card holder and change pouch, all shielded. Measures about 4" x 4½" when folded. Quality European craftsmanship, equally attractive for men and women.
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The power does come from the reader in the form of a low frequency, unmodulated RF signal (a sine wave) around 140 kHz (a very, very low frequency). An antenna on the RFID chip absorbs this RF energy into a capacitive component and the energy from each pulse of the low frequency "Activates" the chip to emit its information on a higher frequency (varies, from 400 MHz to 3 GHz, but mostly in the 400 MHz or 920 MHz bands, depending on the chip design).
The power with which the chip emits its information is dependent on the size of the capacitor on it, so feeding a higher "power beam" to it will not increase the output power.
However, RF energy decreases as the distance from the radiator increases (inverse square law), but does not technically (theoretically) go away completely at any distance from the radiator. If your subversive reader had a higher-gain receiving antenna than the official reader, then you would be able to read the data farther away than one inch.
Note that RFID chips have come a long way since the beginning and now can perform whole two-way transactions during each pulse of activity. The devices could implement a challenge-response type of authentication. The chip sends a string, the reader encrypts it with the secret code, and sends it back to the chip which checks to see if the string is encrypted correctly. If it is, then it sends the data (also enrypted) to the reader, all in one pulse from the "power beam".
While nothing can be totally secure AND also accessible to everyone, the challenge-response system is practical and effective (some mail servers use it so you can log into your mail server over an unencrypted channel without revealing your password).