P5DF081_SDS

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Objective short data sheet

PUBLIC

Rev. 1 — 12 August 2010

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NXP Semiconductors

P5DF081

MIFARE SAM AV2

8.6.3 Data processing commands

SAM_DumpSessionKey

The command SAM_DumpSessionKey can only be used to retrieve the session key of an

established authentication with a DESFire or MIFARE Plus PICC. So an active PICC

authentication (for these card types) is required.

The session key can be retrieved in plain or encrypted, depending on the SAM-Host protection

mode of the logical channel. In Plain and MAC Protection mode, the dump is done in plain; in Full

Protection the key is encrypted (as any other response data field). Under MAC Protection, the

response data field can optionally be encrypted if requested via setting bit 0 of P1.

This command cannot be used for secret key dumping.

SAM_DumpSecretKey

SAM_DumpSecretKey allows dumping any of the PICC keys (except MIFARE Classic

keys) or OfflineCrypto keys.

SAM_DisableKeyEntry

In AV2 mode, two possibilities are supported, similar to the SAM_ChangeKeyEntry

command. Which possibility is used depends on the key class of the change key.

Change keys are either Host Keys or OfflineChange Keys. The second class will allow

offline command generation.

Table 7.

Command

Description

Table 8.

Data processing commands

Command

Description

AV1 compatibility mode

SAM_Verify_MAC

The SAM_Verify_MAC command verifies the MAC which was sent by the DESFire PICC or any

other system based on the given MACed plain text data and the currently valid cryptographic key.

The applied MAC algorithm depends on the key typ.

The command can also be used for verifying only a part of a MAC. The number of MAC bytes to be

verified is defined by parameter P2.

SAM_Generate_MAC

The SAM_Generate_MAC command creates a MAC which is meant to be sent to the DESFire

PICC or any other system based on the given plain text data and the currently valid cryptographic

key.

The applied MAC algorithm depends on the key type.

SAM_Decipher_Data

The SAM_Decipher_Data command deciphers data packages sent by a DESFire PICC,

any other system or a MIFARE card based on the currently valid cryptographic key and

returns plain data to the PCD.

SAM_Encipher_Data

The SAM_Encipher_Data command creates data packages which are meant to be sent to a

DESFire PICC or any other system based on the given plain text data and the currently valid

cryptographic key.

To do so, the plain data is en-ciphered in cipher block chaining send mode. CRC and padding

bytes are appended automatically.

AV2 Mode

The MIFARE SAM AV1 supported the execution of cryptographic operations (MACing, encryption) using the SAM data

processing commands with a key that allowed "Crypto with secret key". So the same primitives as used for the DESFire

communication are also accessible for so-called offline cryptographic operations (i.e. crypto operations that are not part of

the SAM-Host or SAM-PICC communication protocols).

For the MIFARE SAM AV2 this kind of functionality is still supported. The "Crypto with secret key" operation is replaced by a

separate key class, called OfflineCrypto Keys. The existing SAM data processing commands are extended to support full

length MAC generation and verification; also new commands for executing standard CBC encryption and decryption are

provided.

The existing SAM data processing commands (SAM_Generate_MAC, SAM_Verify_MAC, SAM_Encipher_Data and

SAM_Decipher_Data) can still be used to support DESFire communication, by issuing them in an LC with an active PICC

authentication (SAM_AuthenticatePICC). These commands and the new SAM_EncipherOffline_Data and

SAM_DecipherOffline_Data can be used with OfflineCrypto Keys if issued in an LC with an active OfflineCrypto key.