Hello. For SHA-1 verified boot first sector needs to check the rest of
core.img. It will need heavy modifications. On the same time I would
like to avoid changes to current boot process so that both alternatives
are available (SHA-1 and plain boot). In the same time even in current
design the first sector plays a special role. So I propose first sector
to be moved to a separate file and then at install time grub-mkimage or
grub-setup can take care of choosing right one depending on options
supplied by user (plain or SHA-1 boot)