This may be a dumb question, but is there any reason why scp a at b:c d: fails, where scp a at b:c . scp c d: succeeds? I get "Host key verification failed.". I'm using nothing more complex than RSA authorized_hosts based authentication. I'm seeing this on openssh-client 1:5.8p1-1ubuntu3 and OS-X 10.6 OpenSSH_5.2p1, OpenSSL 0.9.8r 8 Feb 2011. -- Alex Bligh