NXP Semiconductors MWCT101 S Series, Reference Manual

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32.5.13.11 CMD_VERIFY_MAC
The Verify MAC command verifies a MAC of a given MESSAGE, which can be
multiple 128-bit blocks of data, against a provided for MAC. The MESSAGE to
compare, starting with the leftmost bit of the MAC, are given in the
MESSAGE_LENGTH. The value 0 is not allowed and is interpreted by SHE to compare
all bits of the MAC. The function returns an error if the length provided for message has
another length than stated in MESSAGE_LENGTH. Input DATA1-DATAn until all
messages are entered, with the expected MAC being the last entry after all DATA are
input, i.e., MAC will be the position of block N+1 for 'N' number of DATA blocks.
All padding is to be done according to SHE specification using MESSAGE_LENGTH.
n = CEIL(MESSAGE_LENGTH / 128)
The first example shows 6 DATA blocks followed by the expected MAC, with the output
overwriting the DATA1 block at the end of the operation with the MAC verification
status.
The continuation examples show DATA1-10 by continuing from the first example but
DATA7 would be written in place of the CMAC from the first example, followed by
continuation with DATA8 which follows on the next page. Finally ending in DATA10
for this example, following with the expected CMAC value after the DATA 10 entry.
Table 32-71. Verify MAC command details
Parameter Direction Width
KEY_ID IN 5
MESSAGE_LENGTH IN 32
MESSAGE (DATA <n>) IN n * 128
MAC IN 128
MAC_LENGTH (MAC Length[6:0]) IN 7
VERIFICATION_STATUS (Verification Status[0]) OUT 1
MAC
calc
= TRUNCATE(CMAC
KEY, KEY_ID
(MESSAGE, MESSAGE_LENGTH), MAC_LENGTH)
MAC
ref
= TRUNCATE (MAC, MAC_LENGTH)
VERIFICATION_STATUS = (0 ~= ( MAC
calc
- MAC
ref
))
Error Codes: ERC_NO_ERROR, ERC_SEQUENCE_ERROR, ERC_KEY_NOT_AVAILABLE,
ERC_KEY_INVALID,ERC_KEY_EMPTY, ERC_MEMORY_FAILURE, ERC_BUSY, ERC_GENERAL_ERROR
Figure 32-33. Verify MAC input parameters
Functional description
MWCT101xS Series Reference Manual, Rev. 3, 07/2019
798 NXP Semiconductors