The four 32-bit Intermediate Hash Word registers expose the
intermediate GHASH value. May be read to save the current GHASH value so processing
can later be resumed, presumably on a later message fragment. Whenever a new key is
written to the AES Key Register two automatic actions are processed:
- GCM hash subkey generation
- AES_GHASHRx Clear
Refer to the Key Writing and Automatic Hash Subkey Calculation for details.
If an application software-specific hash initial value is
needed for the GHASH, it must be written to AES_GHASHRx:
- After a write to the AES Key
Register, if any,
- Before starting the input data
feed.
