passwdqc - password/passphrase strength checking and enforcement

passwdqc is a password/passphrase strength checking and policy
enforcement toolset, command-line programs (pwqcheck and pwqgen),
and a library (libpasswdqc).

pwqcheck and pwqgen are standalone password/passphrase strength
checking and random passphrase generator programs, respectively,
which are usable from scripts.

pam_passwdqc is a simple password strength checking module for
PAM-aware password changing programs, such as passwd(1).

libpasswdqc is the underlying library, which may also be used
from third-party programs.

To enable pam_passwdqc in Slackware you need to replace any other
password strength checking PAM modules like pam_pwquality.so in
/etc/pam.d/system-auth with the following line:

password    requisite     pam_passwdqc.so