This question is in the HP-UX forum and the OP even explicitly mentions HP-UX. There is no /etc/login.defs on any version of HP-UX. I have seen it on Linux though.
The security manpage and the features described on it arrived with HP-UX 11i. It is not available on earlier versions.
You may be interested to know that HP-UX 11i can support
Shadow Passwords. Read the page I linked carefully before you proceed, stuff like pc-nfs and sam will not work with shadow passwords.
And you may be interested in
this post.