NXP Semiconductors

MF1P(H)x1y1

MIFARE Plus EV1

MF1P(H)x1y1

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Product short data sheet

Rev. 3.2 — 6 December 2018

COMPANY PUBLIC

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8.5 Transaction MAC

The Transaction MAC feature helps preventing fraudulent merchant attacks. In example,

it allows a merchant operating a point-of-sale terminal to prove that the transactions he

executed with customers are genuine towards the back-end system. This is done by

letting the card generate a Transaction MAC over the transaction with a key shared only

by the card and the back-end system. The Transaction MAC feature can be activated

block by block. Note that the pre-personalization of the card has to be done by the card

issuer and not by the merchants provider.

MAC generation also involves a Transaction MAC Counter maintained by the card,

which allows the back-end system to detect replay attempts by the merchant. In addition,

this counter allows the back-end system to detect missing transactions, which in turn

allows detecting fraud where in example the merchant has increased the balance

without reporting the transaction. Note that a counter also allows for easier detection

mechanisms of replay than keeping logs with fingerprints of every transaction.

As only fraud detection might not be sufficient if one cannot point to the fraudulent

merchant, an additional configuration option allows the back-end to require that the

merchant’s terminal commits its identity, called ReaderID, during the transaction. This

requires support of a SAM which allows secure commit of its UID.

The card supports linking ReaderIDs of merchants by storing the committed ReaderID

and returning the ReaderID of the previous transaction. This way the back-end system

can detect which merchant did not report missing transactions.