MM code

An MM code (the "MM" being an abbreviation for the German "Moduliertes Merkmal") is a "machine-readable modulated" feature that has been added to German debit cards during manufacture as an anti-counterfeiting measure since 1979. It was developed by "Gesellschaft für Automation und Organisation" (a subsidiary of Giesecke & Devrient) in Munich for the German ec-Card system and MM verification devices have been added to German ATMs from 1982 onwards. If a payment card contains an MM code as well as a magnetic stripe, any fraudster who counterfeits the card but fails to read and duplicate the MM code onto the copy will be detected when trying to use the counterfeit in a German automated teller machine.

An MM code (the "MM" being an abbreviation for the German "Moduliertes Merkmal") is a "machine-readable modulated" feature that has been added to German debit cards during manufacture as an anti-counterfeiting measure since 1979. It was developed by "Gesellschaft für Automation und Organisation" (a subsidiary of Giesecke & Devrient) in Munich for the German ec-Card system and MM verification devices have been added to German ATMs from 1982 onwards. If a payment card contains an MM code as well as a magnetic stripe, any fraudster who counterfeits the card but fails to read and duplicate the MM code onto the copy will be detected when trying to use the counterfeit in a German automated teller machine. ==Function== Automated Teller Machines which can read the MM code contain a special MM box and sensor to read and verify the MM code. The MM box was for a long time considered a well-guarded secret; cash machine manufacturers do not access or service the box. The MM code consists of two components, one stored on the magnetic stripe, and one hidden inside the card's material. During MM code verification, a cryptographic operation is performed to check that the MM code on the magnetic stripe corresponds to the hidden one. The presence of the keyed cryptographic operation means that the correct MM code for a counterfeit cannot be calculated from the magnetic stripe information alone without knowledge of the key – it must be read from the original card itself. In order to remain effective, the MM code relied on the obscurity of the reading mechanism and the expense and difficulty of embedding a code once known. Since the arrival of the EMV chip-based payment protocols, the MM code has reduced significance in combatting card counterfeiting. ==References==

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