the incorrect key length (usually "1024") with the correct key length
(usually "1023").
+5. Spurious PAM authentication messages in logfiles
+
+OpenSSH will generate spurious authentication failures at every login,
+similar to "authentication failure; (uid=0) -> root for sshd service".
+These are generated because OpenSSH first tries to determine whether a
+user needs authentication to login (e.g. empty password). Unfortunatly
+PAM likes to log all authentication events, this one included.
+
+If it annoys you too much, set "PermitEmptyPasswords no" in
+sshd_config. This will quiet the error message at the expense of
+disabling logins to accounts with no password set. This is the
+default if you use the supplied sshd_config file.