"obscure" in /etc/pam.d/common-password what does it mean exactly?

[prosolutions@gmx.net]

I've scoured through all Debian pam documentation, upstream PAM docs,
and did extensive googling but cannot find the definition of "obscure"
as it applies to common-password.  Anyone have any info on this?


I am assuming this is where the default system password policy is set:


password   required   pam_unix.so nullok obscure min=4 max=8 md5