MM code: Difference between revisions

Revision as of 11:47, 10 January 2008

Revision as of 12:15, 10 January 2008

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The "'''MM Code"code''' is a shortmachine-readable numberfeature writtenadded physicallyto on a credit orGerman debit cardcards during manufacture, hiddenas usingan anti-[[Steganographycounterfeiting]], adoptedmeasure. It was developed by "Gesellschaft für Automation und Organisation" in Munich for the German bankingec-Card industrysystem and was added to fightGerman cardATMs from 1982 onwards.<ref name="ct1996">Carsten Meyer: [http://www.heise.de/ct/96/07/094/ Nur Peanuts – Der Risikofaktor Magnetkarte]. [Counterfeiting[c't]] 7/1996, p. 94</ref> 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 on to the copy will be detected when trying to use the counterfeit in an [[Automated Teller Machine]].

Automated Teller Machines which can read the MM code contain a special MM box which contains the circuitry to read the MM code. This box sits more than an inch away from the card. It is unclear whether the MM code is read optically from a distance during acquisition of the card from the slot, or if there is some kind of read head positioned closer to the card and connected to the MM Box. 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. 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.

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A third class considers encoding the code using the electrical properties of the plastic card, such as capacitance. Such an explanation requires a read head within close proximity to the card.

==References==

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