| 摘要 |
A payment card comprises a plastic card with a magnetic stripe for user account data. Internal to the plastic card, and behind the magnetic stripe, a number of fixed-position magnetic write heads allow the user account data to be automatically modified. For example, a data field that counts the number of times the card has been scanned is incremented. A payment processing center keeps track of this usage-counter data field, and will not authorize transaction requests that come out of sequence. For example, as can occur from a magnetic clone of a card that has been skimmed and tried later. A card-swipe detector embedded in the plastic card detects each use in a scanner, and it signals an internal microcomputer which changes data bits sent to the write heads. Once scanned, the payment card can also disable any reading of the user account data for a short fixed period of time.
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