Checking New Password

[Zen]

Hi,

Being new to BSD I was wandering if someone can point me in the correct
direction.  I want to let users to change their own passwords.  But I do not
want them to use things like cat dog or dictionary names.  Could some one
point me in the correct direction please.  I would like to use some thing
like 6-8 characters with number and upper and lower case letters

Thanks

Zen