This part of the CentOS 5 server setup howtos will show you how to configure OpenSSH to enable secure, key-based password-less authentication as well as user jail rooting. OpenSSH's internal SFTP server will also be configured for enabling fast and secure file transfers to the server.
As of writing, the most recent version of CentOS available is 5.6 so I will be using it as the basis for this howto. If a newer version is available, I recommend you use that version instead. Much of these instructions should still apply, especially if it is only a newer 5.x release.