Commission Implementing Regulation (EU) 2016/799Show full title

10.5.2 Secure Message Structure U.K.

CSM_188 Secure Messaging shall make use only of the Secure Messaging data objects (see [ISO 7816-4]) listed in Table 5. In any message, these data objects shall be used in the order specified in this table. U.K.

Table 5
Secure Messaging Data Objects
Data Object Name	Tag	Presence (M)andatory, (C)onditional or (F)orbidden in
		Commands	Responses
Plain value not encoded in BER-TLV	‘81’	C	C
Plain value encoded in BER-TLV, but not including SM DOs	‘B3’	C	C
Padding-content indicator followed by cryptogram, plain value not encoded in BER-TLV	‘87’	C	C
Protected Le	‘97’	C	F
Processing Status	‘99’	F	M
Cryptographic Checksum	‘8E’	M	M

Note: As specified in Appendix 2, tachograph cards may support the READ BINARY and UPDATE BINARY command with an odd INS byte (‘B1’ resp. ‘D7’). These command variants are required to read and update files with more than 32 768 bytes or more. In case such a variant is used, a data object with tag ‘B3’ shall be used instead of an object with tag ‘81’. See Appendix 2 for more information. U.K.

CSM_189 All SM data objects shall be encoded in DER TLV as specified in [ISO 8825-1]. This encoding results in a Tag-Length-Value (TLV) structure as follows: U.K.

Tag

:

The tag is encoded in one or two octets and indicates the content.

Length

:

The length is encoded as an unsigned integer in one, two, or three octets, resulting in a maximum length of 65 535 octets. The minimum number of octets shall be used.

Value

:

The value is encoded in zero or more octets

CSM_190 APDUs protected by Secure Messaging shall be created as follows: U.K.

• The command header shall be included in the MAC calculation, therefore value ‘0C’shall be used for the class byte CLA.

• As specified in Appendix 2, all INS bytes shall be even, with the possible exception of odd INS bytes for the READ BINARY and UPDATE BINARY commands.

• The actual value of Lc will be modified to Lc' after application of secure messaging.

• The Data field shall consist of SM data objects.

• In the protected command APDU the new Le byte shall be set to ‘00’. If required, a data object ‘97’ shall be included in the Data field in order to convey the original value of Le.

[F1 CSM_191 Any data object to be encrypted shall be padded according to [ISO 7816-4] using padding-content indicator ‘01’. For the calculation of the MAC, data objects in the APDU shall be padded according to [ISO 7816-4]. U.K.

Note: Padding for Secure Messaging is always performed by the secure messaging layer, not by the CMAC or CBC algorithms. U.K.

Textual Amendments

F1 Substituted by Commission Implementing Regulation (EU) 2018/502 of 28 February 2018 amending Implementing Regulation (EU) 2016/799 laying down the requirements for the construction, testing, installation, operation and repair of tachographs and their components (Text with EEA relevance).

Summary and Examples U.K.

A command APDU with applied Secure Messaging will have the following structure, depending on the case of the respective unsecured command (DO is data object):

Case 1

:

CLA INS P1 P2 || Lc' || DO ‘ 8E ’ || Le

Case 2

:

CLA INS P1 P2 || Lc' || DO ‘ 97 ’ || DO ‘ 8E ’ || Le

Case 3 (even INS byte)

:

CLA INS P1 P2 || Lc' || DO ‘ 81 ’ || DO ‘ 8E ’ || Le

Case 3 (odd INS byte)

:

CLA INS P1 P2 || Lc' || DO ‘ B3 ’ || DO ‘ 8E ’ || Le

Case 4 (even INS byte)

:

CLA INS P1 P2 || Lc' || DO ‘ 81 ’ || DO ‘ 97 ’ || DO ‘ 8E ’ || Le

Case 4 (odd INS byte)

:

CLA INS P1 P2 || Lc' || DO ‘ B3 ’ || DO ‘ 97 ’ || DO ‘ 8E ’ || Le

where Le = ‘ 00’ or ‘00 00 ’ depending on whether short length fields or extended length fields are used; see [ISO 7816-4].

A response APDU with applied Secure Messaging will have the following structure, depending on the case of the respective unsecured response:

Case 1 or 3

:

DO ‘ 99 ’ || DO ‘ 8E ’ || SW1SW2

Case 2 or 4 (even INS byte) without encryption

:

DO ‘ 81 ’ || DO ‘ 99 ’ || DO ‘ 8E ’ || SW1SW2

Case 2 or 4 (even INS byte) with encryption

:

DO ‘ 87 ’ || DO ‘ 99 ’ || DO ‘ 8E ’ || SW1SW2

Case 2 or 4 (odd INS byte) without encryption

:

DO ‘ B3 ’ || DO ‘ 99 ’ || DO ‘ 8E ’ || SW1SW2

Note: Case 2 or 4 (odd INS byte) with encryption is never used in the communication between a VU and a card. U.K.

Below are three example APDU transformations for commands with even INS code. Figure 8 shows an authenticated Case 4 command APDU, Figure 9 shows an authenticated Case 1/Case 3 response APDU, and Figure 10 shows an encrypted and authenticated Case 2/Case 4 response APDU.

Figure 8

Transformation of an authenticated Case 4 Command APDU

Figure 9

Transformation of an authenticated Case 1 / Case 3 Response APDU

Figure 10 Transformation of an encrypted and authenticated Case 2/Case 4 Response APDU U.K.

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