host keys authentication

[Johan Booysen]

I have an FTP server using SSH for secure file uploads/downloads.  Users
are chrooted into their home directories, and it works very well.

Now we have the requirement that a client wants to upload/download via
some or other automated process or script, so I need to work out how to
do that via host keys or something similar.  I understand generating
keys using ssh-keygen, and so on, but I'm not sure of the specifics of
allowing a user or machine on the client side to automatically
authenticate using public keys, and making sure that they are then still
chrooted into their home folder on the FTP server.

Can anyone point me in the right direction?  I've been googling it, but
haven't really hit upon a good source of information for this kind of
setup yet.

Much appreciated.