Ballot Casting Assurance

We propose that voting protocols be judged in part on ballot casting assurance, a property which complements universal verifiability. Some protocols already support ballot casting assurance, though the concept has not received adequate explicit emphasis. Ballot casting assurance captures two well known voting concepts – cast as intended, and recorded as cast – into one end-to-end property: Alice, the voter, should obtain immediate and direct assurance that her intended vote has “made it” into the tally. We review Neff’s scheme, MarkPledge, and show that it provides ballot casting assurance. We also briefly show how Chaum’s “Punchscan” system also provides ballot casting assurance, though under more complicated deployment assumptions. We show how ballot casting assurance opens the door to realistic failure detection and recovery in the middle of an election, a topic which has been ignored in much of the voting literature.