Use of Block RAM (BRAM) for storage of constants [8]. Reconfigurable hardware devices
such as FPGAs often have on-board memories which can be pre-loaded.
Storing the Kt constants in these memories frees up space in the device
which can then be used to implement extra logic. The free space also leads to
improved routing and, thus, a general speed-up in circuit operation.
                                                         
From "Optimisation of the SHA-2 Family of Hash Functions on FPGAs"
Robert P. McEvoy, Francis M. Crowe, Colin C. Murphy and William P. Marnane
             Department of Electrical & Electronic Engineering,
                      University College Cork, Ireland
             {robertmce, francisc, cmurphy, liam}@rennes.ucc.ie