How to check password encryption in cookie?

if we want to check password encryption then how to check in cookie?
n is it so that we can check pwd encryption only if we have allowed to get our pwds saved i.e. when msg apperars for the 1st time when we login in a new site or we can check without using that saving pwds by checking in our system.
if we have to check in our system (some txt file is there) then how to check encryption
hope i m clear 2 u