If you want to verify a password, you can find your answer here.
Not possible by standard Mendix alone. The password can only be validated but in no way the password can be used to retrieve any other data. Thus the user will need to enter something other the just a password, likely her userid.
Your best shot is to suggest other solutions like the browser's credential-storage-functions to store a userid and password. Or better have the users use a passwordmanagement tool like keepass or lastpass.
Hopefully Rom's solution works for you. Then you are no longer entering a password, but a (sort of) certificate.