Question about Server Authentication

[Steeve BARBEAU]

Hi guys,

I'm working on a project which concern SSH and there is something i don't understand about server authentication. So I explain my problem:

- When you authorize only RSA keys in the sshd_config on the server, you need to have the RSA public key of this server in the known_hosts file of the client. This is absolutely normal.

- When you authorize only DSA keys in the sshd_config on the server, you need to have the DSA public key of this server in the known_hosts file of the client. This is also absolutely normal.

- But when you authorize both RSA and DSA keys, you are obliged to have the RSA public key in the known_hosts file, without it fails. If there is only DSA in the known_hosts file it fails, and this is that I don't understand. Why the server authentication doesn't work with the DSA key when both DSA and RSA are authorize. (Of course if both are present in the known_host file, it works). So if somebody can help me about this, it will be nice ;)
I've read lot of documentation, a little the 4 RFC but I haven't found the answer to my question.

Steeve