When we get to actually electing representatives to the democratic world parliament (DWP), will we need to use a secret ballot?
Yes, for democratic world parliament (DWP) elections, a secret ballot must be used, because that is one of the pillars of any effective democracy. (It is possible that by the time that first real global election rolls around in 2018 or whenever, there will be ironclad ways to prevent multiple voting without the expense and trouble of a global enumeration.