The only file in that directory is known_hosts. I'm not sure why keys would enter into this at all anyway. As I understand it, the whole idea is to just stick the trusted hosts into .rhosts, and you're away.
You want the key placed into the file ~/.ssh/authorized_keys. For example, I have placed the key from each of my client machines into the server, allowing me to login without password. I use the file I mentioned above, and it Just Works (TM).
-Roberto
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