I've several machines at home: A small nas, my notebook, a litte webserver etc.
Some of these machines store my entire digital life - so I encrypted nearly every partition. To boot up the devices, I have to type in about 5 passphrases to different machines.
I'm searching for a small key distribution server: A RPI (or something else) based system which I can boot and unlock first and where the other machine can get their keyfiles from.
The authentication could be done by SSH key auth or x509-auth over HTTPs. As a bonus the machines may automatically lock the partitions if the keyserver is unreachable for a specific amount of time or sends some kind of an emergency signal.
I can't believe that noone developed such a tool...