How to create unique download codes for buyers?

Hi folks,

Im trying to create a website where users can purchase “Vouchers” however each person that puchases them I need them to be given a unique download code which is attached to their receipt to distinguish all my buyers.

For example 10 people purchase a voucher and they need to be send 10 unique download codes that they keep safe and simply hand to the merchant to collect their product or service.

is this possible or is there anything out there that can do this?
Any help would be greatly appreciated!