OpenSSH 3.5p1 (HP version): permissions of public identity

[Ulrich Windl]

Hello,

I just received thes odd messages from HP-UX Secure Shell A.03.50.000. 
(OpenSSH 3.5p1):

# ssh-add id_rsa.pub
5215: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
5215: @         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
5215: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
5215: Permissions 0644 for 'id_rsa.pub' are too open.
5215: It is recommended that your private key files are NOT accessible by 
others.
5215: This private key will be ignored.
5215: bad permissions: ignore key: id_rsa.pub
Enter passphrase for id_rsa.pub:

Now I think the ".pub" is a public key, so what's wrong with the permissions? 
Also, when private key will be ignored, why then ask for a password?

I'm a bit confused.

Regards,
Ulrich