Every citizen has a responsibility to submit a ballot (either valid, invalid, or covered in dicks).
And the state (or in our case an independent electoral commission) has a responsibility to collect a ballot from every voter. Which leads to making it as easy as possible for you to vote, with early voting, mail-in ballots and heaps of polling centres.
The ballot problem is easier than you’d think though. Make effective corruption untenable, by involving a lot of people in the process. Everyone who can gain from the outcome should have equal presence as observers.
And the tangibility of the ballot is crucial, it’s much harder to make 10,000 pieces of paper appear or disappear than to flip a bit.