56.5.16 AES GCM H Word Register x
| Name: | AES_GCMHRx |
| Offset: | 0x9C + x*0x04 [x=0..3] |
| Reset: | 0x00000000 |
| Property: | R/W |
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| H[31:24] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| H[23:16] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| H[15:8] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| H[7:0] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
Bits 31:0 – H[31:0] GCM H Word x
The four 32-bit H Word registers contain the 128-bit GCM hash subkey Hvalue.
Whenever a new key is written to the AES Key Register, two
automatic actions are processed:
- GCM hash subkey H generation
- AES_GHASHRx Clear
If the application software requires a specific hash subkey, the automatically-generated H value can be overwritten in AES_GCMHRx. See Key Writing and Automatic Hash Subkey Calculation for details.
Generating a GCM hash subkey H by a write in AES_GCMHRx enables to:
- select the GCM hash subkey H for GHASH operations,
- select one operand to process a single GF128 multiply.