Just re-tested in latest RC, dCore-jessie:2016.02.19.16.43, notes:
1. Altered md5 file, update check completes almost immediately. Everything works as expected when checking the exension with sce-update , but not when running sce-update -c , provides view package updates option but it does not display any output, just exits:
sce-update -c
.
.
xorg-intel
Press Enter to update check above SCE(s), (q)uit to exit:
Checking xorg-intel.sce...
xorg-intel update check...
Update check completed.
xorg-intel
Press Enter to view package updates, Ctrl-C aborts: v
tc@box:/mnt/sdb4/tce/sce$
Running sce-update then checking xorg-intel, check is quick and everything works as expected:
sce-update
.
.
xorg-intel
Press Enter to update check above SCE(s), (q)uit to exit:
Checking xorg-intel.sce...
xorg-intel update check...
Update check completed.
xorg-intel
Press Enter to update above SCE(s), (v)iew package updates, Ctrl-C aborts: v
xorg-intel updates:
xorg-intel did not pass the md5sum check, needs re-importing..
Press Enter to proceed with updates, Ctrl-C aborts:
2. When booting system get extension loading error, something like 'md5sum error xorg-intel, exiting..', Some sort of error is expected, but it loads anyway despite the error. Wouldn't this be a concern if the SCE was either corrupt or maliciously altered.