SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
The following procedure is used to continue a prior HMAC calculation interrupted from a high priority task (see Table 25-8).
| Step | Register / Bit Field / Programming Model | Value |
|---|---|---|
| Load the initial digest for the used hash algorithm. | SHA_IDIGEST_i[31:0] DATA | - |
| Restore the digest counter with the value before the switch to the high-priority task. | SHA_DIGEST_COUNT[31:0] COUNT | - |
| Use the already loaded in the engine key. | SHA_MODE[5] HMAC_KEY_PROC | 0x0 |
| Do not use the constants of the selected hash algorithm. | SHA_MODE[3] ALGO_CONSTANT | 0x0 |
| Select the SHA-1 hash algorithm. | SHA_MODE[2:1] ALGO | 0x1 |
| IF: This is the last 64-byte data block from the input message? | User decision | - |
| Close the hash; an appropriate padding is added. | SHA_MODE[4] CLOSE_HASH | 0x1 |
| ENDIF | - | |
| Load the block length; this is the trigger to start processing. | SHA_LENGTH[31:0] LENGTH | - |
NOTE
This initial digest is the intermediate digest from the previous calculation before switching to the high priority task. The value is equal to context1 in.
NOTE
The value is equal to context2 in.
NOTE
The block length is equal to the context3 value in.