SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
AES Authentication Data Length (AES_AUTH_LENGTH)
The AES Authentication Data Length (AES_AUTH_LENGTH) register stores the authentication data length in bytes for combined modes only (GCM or CCM). Supported AUTH lengths for CCM are from 0 to (216 - 28) bytes. For GCM any value up to (232 - 1) bytes can be used. Once processing with this context is started, this length decrements to zero. A write to this register triggers the engine to start using this context for GCM and CCM. For XTS, this register is optionally used to load j. Loading of j is only required if j ≠0. j is a 28-bit value and must be written to bits [31-4] of this register. j represents the sequential number of the 128-bit block inside the data unit. For the first block in a unit, this value is zero. It is not required to provide a j for each new data block within a unit. Note that it is possible to start with a j unequal to zero.
NOTE
For a Host read operation, these registers return all zeroes.
AES_AUTH_LENGTH is shown in Figure 9-18 and described in Table 9-12.
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| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| AUTH | |||||||||||||||||||||||||||||||
| R/W-0x0 | |||||||||||||||||||||||||||||||