Matthew Christian asked 3 years ago I have received a replacement credit card and my bank now only issues RFID "tap 'n' go" cards. However, I don't want anything in my wallet that can broadcast a signal I can't control. I'm not worried about credit fraud, just about the RFID chip's serial number being used to gather marketing data about me and my purchases. Can the card's serial number be used as a unique identifier, like Web browser cookies, that will let ads follow me?
—Matthew
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Matthew,
Good question. First, the type of RFID transponder used in a credit card does not broadcast a signal and has no power source. It gets its energy from radio waves emitted by the reader and reflects back a signal to that reader. Some passive tags (those with no battery) can reflect a signal 20 feet or more, but the transponders in credit cards are designed to have a read range of no more than a few inches. The reason for this is so that if two people were paying at adjacent points of sale, the reader from one POS would not pick up the serial number of the card owned by the person at the other. Another reason is so that no one can eavesdrop on the tag-to-reader communication and steal your data.
It would be very difficult to use the number in your card as a personal identifier, given the extremely short read range. Anyone who wanted to track you would need to have a reader within a few inches of your wallet to identify you. Obviously, this would not be practical. If you are still concerned, however, you can simply put a piece of aluminum foil or mylar inside your wallet to block any radio waves from reaching the tag and powering it up.
Yours,
Mark Roberti
Founder and Editor
RFID Journal
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