mission impossible

[=?ISO-8859-1?Q?Kaj_M=E4kinen?=]

Is this secure?
I have set up an authpf on my firewall. When I authenticate with an ssh2 
des keyfile the firewall passes
and  forwards it to my windows computer according to my rules in 
authpf.rules. On my windows computer I run Cygwin sshd also with ssh2 
PubkeyAuthentication.

Of courseI have PasswordAuthentication no , PubkeyAuthentication yes 
and  Protocol 2 in my sshd_config.
An attackeron my open-bsd box gets the login prompt but no password 
prompt withouth the keyfile.
The error is then this:  Received disconnect from xxx.xxx.xxx.xxx 11: No 
supported authentication methods available
Won't this be a mission impossible to hack?