MM code: Difference between revisions

Revision as of 05:38, 12 June 2020

Revision as of 14:32, 18 November 2020

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==Function==

[[File:Mmcode.png|thumbnail|Diagram showing verification of the MM Code.]]

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.