Right, but there's no real proof the dropbear/sh/etc. you talk to is untampered after reboot; it could easily be logging, if someone shut your system down and r

Right, but there's no real proof the dropbear/sh/etc. you talk to is untampered after reboot; it could easily be logging, if someone shut your system down and replaced the boot drive. ssh vs. serial console at least requires they extract some (unencrypted) key from the drive, though.