[tptacek]

No, SPA is the first picture: both SPA and OpenSSH are directly responsive to attacker communications. I don't think "attack surface" is the dispositive argument here (the fact that SPA doesn't protect OpenSSH connections at all is), but either way: SPA is inferior to spiped.

[michaelrash]

Not exactly. OpenSSH gated by SPA can only be interacted with by an attacker that can either hijack an SPA-authenticated connection, or is on the same network as the SPA client if the client must go through a NAT. This is a fairly limited set of possible attackers. For those not in this set, how can they interact with OpenSSH without first breaking SPA?