I want to automatically generate vouchers with only password for the users that i just have registered.
This password must be used with the existent username o my users.
Users can buy the vouchers with the password, login with their fixed username but using password of the voucher.
thank you
how will you know which password is for which user ? 
The problem is just this, i want to give password that can be used by any user. So passwords are not linked to a particular user.
I have a group of users with their username. I want to create vouchers of password and sell it to the users, i sell only the password that infact is not linked to a user. A user buy the password and insert his username and password to login.
instead, make random usernames with no password. let your login page have only the username field, hide the password field.
as explained above, i need fixed username (i have fixed ip linked to respective username), so i need random password. (see my previous message).
what is the difference, username or password, if you will only use one of the above 
it doesn’t matter what you call it, “access code” even the result will be the same
ok, but i have the fixed public ip address in the user data. i think it is linked to username… or not?
you can’t have the same IP for all users
infact i have a public fixed ip adress for every user.
I think he want something like GSM/CDMA prepaid voucher..
Vouchers has a separated table and contains the period of validity. Each person has their own fixed GSM/CDMA phone number, but when he entered the grace period, he was obliged to purchase prepaid vouchers to extend the use of their phone number.
In this case, fixed phone number is the username(and password), and prepaid voucher is the password that contains the period of validity(just like ‘extend’ feature, but more flexible). I would be very happy if this way of working can be applied in the usermanager.
Correct Me If I’m Wrong
Dear normis. I think what he wants to know and probably me is this.
Can usermanager generate prepaid vouchers(scratch cards in the case of GSM) that when an existing user signs in with their existing username and password, they can go to their profile page and insert the prepaid voucher and in turn obtain an uptime extension or etc.
So its logical that thiese prepaid vouchers or scratch cards have only a code. Instead of another username and password.
Netadoo
something like top up cards?
you refill your existing account with top up card/code