On a similar theme, I'd like to know if there's a secure and sensible way to SSH using a "shared" key in two parts. Because it seems the flaw is having to trus

On a similar theme, I'd like to know if there's a secure and sensible way to SSH using a "shared" key in two parts. Because it seems the flaw is having to trust this combination of an IP and its fingerprint is suitable for many purposes but not all -- and that's the underlying thing we are all fighting here. For transient systems I'd like to be protected that the only trust comes with the two private keys from a home directory at either side. At first glance it seems you may use (abuse) "authorised_keys" and the public key for this purpose, by switching off host key checking. However this is invalid if SSH actively presents the public key to the peer.