We want to send files around between some linux hosts via OpenSSH, but we don't want clients to be able to list / retrieve / modify existing files on the server.
In other words, it should be an "upload only" service working over the ssh protocol. Of course this means there will always be a way for the client to know if there is already a file with a given name on the server, that's ok as far as the file contents cannot be retrieved.
How could we achieve this, possibly using already established softwares available in common distributions?