@GM: I was going on by the 'kindle touch' in his profile

. But, yeah, to be completely clear: it only installs the kindlet keys on a K4/K5. For every other devices, use ixtab's devkey installer

. And it is indeed completely safe to reinstall the keystore, unless you modified it somehow and forgot to back it up, of course

.
EDIT: Scratch that, it installs the kindlet keys on every Kindle FW, but I'm not sure if someone distributed a properly packaged version of it for non K4/K5 devices.