ThreeBallot in the Field

Voting systems have been the subject of much recent controversy. Due to the difficulty of securing and auditing electronic voting systems, a variety of different paper- based cryptographic voting schemes have emerged. Ronald Rivest has proposed a purely paper-based system called ThreeBallot, which strives to achieve the same level of security as cryptographic systems without using cryptography. Although ThreeBallot has been subject to academic criticism, it has not been tested in the field. This paper describes a paper-based and a computer-aided implementation of ThreeBallot. Any successful voting system must be usable, must be secure, and must preserve the secret ballot. To test usability, we held mock elections and observed voters. To test security and privacy, we executed attacks against these mock elections. In one mock election, 20% of voters successfully sold their vote. One student, when given control of tallying the votes, was able to throw the entire election. In our usability studies we confirmed voter difficulty in using ThreeBallot. Wefound that about 10% of voters didn't understand ThreeBallot well enough to check another's ballot, and in one mock election more than 30% of voters failed to cast a valid ballot on their first try.