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 in AES_KEYWRx, two automatic actions are processed:
- GCM hash subkey generation
- AES_GHASHRx Clear
See 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 writing AES_KEYWRx, if
any
- before starting the input data
feed.