scp user@fromhost:file user@tohost:file
Enter passphrase for RSA key:
The coolest thing about scp is that you don't have to be ON fromhost to copy
files between it and tohost. If passwords or RSA authentication passphrases
are needed you will be prompted for them by scp.
It's also interesting to note that there is no unix password needed for ssh
with RSA auth. Your password field in /etc/shadow can be "*" or "!" or
whatever your particular OS uses to signify an account which has a locked
password.
--Adam