I would like to write a survey script for a target group of people that allows my users to reply anonymously - at the same time, I don't want there to be duplication (i.e. I don't want someone to be able to submit a response to the survey twice.)
What I had in mind was to issue each individual a unique code, say, XYZ, and then have them type in a code of their liking, say ABC. The idea is then have a script which is able to read the properties of the compound code XYZABC and determine that the code was indeed issued from me, without actually being able to identify XYZ specifically.
Does anyone have any ideas on how this can be done?