P5DF081 datasheet(11/36 Pages) NXP

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P5DF081_SDS

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Objective short data sheet

PUBLIC

Rev. 1 — 12 August 2010

191710

11 of 36

NXP Semiconductors

P5DF081

MIFARE SAM AV2

8.4.5 Key versioning

The MIFARE SAM AV2 reserves three bytes in a key entry to store the version of the three

available keys in the entry. This version byte contains the key version for all kinds of keys

(DES, TDEA, AES and MIFARE). The version information must be included separately in

every key entry of type AES or MIFARE when it is updated by the ChangeKeyEntry

command.

8.4.6 Key usage counters

In order to count and limit the number of authentications a key entry can be used for,

MIFARE SAM AV2 stores a table of 16 key usage counter entries, 00h to 0Fh, which are

automatically incremented each time a defined key entry is used for authentication.

Multiple key entries can use the same counter.

8.4.6.1

Reference number

The property RefNoKUC codes the reference number of the key usage counter.

RefNoKUC is the index of the entry in the table and can have the value 00h to 0Fh,

therefore 16 key usage counters can be stored.

8.4.6.2

Limit

This field stores the current limit for this key usage counter. It is only possible to use a key

that is linked to this counter for authentication if the current value (see below) is smaller

than the current limit. As soon as the current value is equal to, or higher than, the current

limit, the usage of all key entries linked to this counter is prohibited.

8.4.6.3

Key reference number to change the current KUC entry

In order to change the KUC, a successful authentication by the host application of the

MIFARE SAM AV2 is necessary. The KeyNoCKUC defines the reference number of the

KST which is used for this.

8.4.6.4

Key version to change the current KUC entry

The 1-byte field holds the key version within the key entry specified to change the KUC

entry. The key version has to be in the range of 00h to FFh. The MIFARE SAM AV2 will

automatically select the appropriate key from one of three positions in the entry that has

the specified version number.

8.4.6.5

Current value

The CurVal field stores the current value of this key usage counter. It is possible to use all

keys referring to this counter for authentication only if the current value is smaller than the

current limit.

8.5 SAM - Host communication

8.5.1 General principles for SAM-Host protection

MIFARE SAM AV2 supports two different modes: AV1 compatibility mode and MIFARE

SAM AV2 mode. A MIFARE SAM AV2 is initially in MIFARE SAM AV1 compatibility mode.

It can be switched to the MIFARE SAM AV2 by executing a host authentication with the

SAM Master Key using the SAM_LockUnlock command. Note that MIFARE SAM AV2

mode activation is thus only possible if the SAM Master Key is configured as an AES128

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