Annex A (normative) UADP Header Layouts

A.2 Message headers for periodic data with fixed layout

A.2.5 Header layout for NetworkMessages with integrity (signing)

UADP messages may be signed to ensure integrity. In this case the SecurityHeader and the Signature have to be added to the message. See clause 7.2.2.4.3 for a complete description of the signing mechanism.

This header layout is basically the same as the header layout defined in A.2.4 but with additional security level ‘signing but no encryption’.

The NetworkMessage header layout with signing is shown in Figure A.2.

Table A.3 shows the configuration for the NetworkMessage header with signing. The table contains only the added or modified rows from Table A.1.

Table A.3 – UADP NetworkMessage header layout with integrity (signing)

Name	Type	Restrictions
ExtendedFlags1	Byte	Bit 4: Security enabled
SecurityHeader
SecurityFlags	Byte	Bit 0: NetworkMessage Signed enabled   Bit 1: NetworkMessage Encryption disabled   Bit 2: SecurityFooter disabled   Bit 3: Force key reset disabledBit range 4-7: Reserved
SecurityTokenId	IntegerId	The ID of the security token that identifies the security key in a SecurityGroup.
NonceLength	Byte	8
MessageNonce	Byte[8]	A number used exactly once for a given security key.