Something like:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

The RSA host key for xxx.local has changed,
and the key for the according IP address xxxx
is unchanged. This could either mean that
DNS SPOOFING is happening or the IP address for the host
and its host key have changed at the same time.
Offending key for IP in /Users/admin/.ssh/known_hosts:x
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx.
Please contact your system administrator.
Add correct host key in /Users/admin/.ssh/known_hosts to get rid of this message.
Offending key in /Users/admin/.ssh/known_hosts:x
RSA host key for xxx.local has changed and you have requested strict checking.
Host key verification failed.

You probably just tried to login to your iPhone using an (DHCP) WiFi IP-address that was in use by some other iPhone before. Or you try to log into your iPhone using the iPhone name (e.g. iPhone.local) instead of an IP-address.

If you are sure there is no other party on your WiFi network and no DNS spoofing possible the solution is quite easy: Just delete the known_hosts file on your host computer by typing in: rm ~/.ssh/known_hosts