openssh unix dev - Sep 2001 - openssh with s/keys

Hello,

I am going to upgrade my openssh installation and would like to know some
details about its support of s/keys, which are not clear for me from the
on-line manual. 
 - Am I right that 'challenge response authentication' is actually s/key
authentication?
 - Is it possible to enable s/key authentication but disable password
authentication? It was not allowed in OpenSSH_2.2.0/FreeBSD which I use
now.

Thanks,
Alex

PS Please cc: me your reply