ThreeBallot

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A sample ThreeBallot multi-ballot, with a first race for President with candidates Jones, Smith, and Wu and a second race for Senator with candidates Yip and Zinn.

ThreeBallot is a voting protocol invented by Ron Rivest. ThreeBallot is a voting system that can in principle be implemented on paper; the goal in its design was to provide some of the benefits of a cryptographic voting system without using cryptography.

This theoretical system's goals include:

Each voter's vote is secret, preventing vote-selling and coercion.
Each voter can verify that his vote was not discarded, and was correctly used and not altered, in the computation of the election result. (And if not, the voter is in a position to prove the vote counters cheated.)
Everybody can verify the election result was computed correctly.
Everybody can verify that extra fake "voters" were not added, and the full list of voters is publically known.
The method is designed for use with paper ballots and requires primarily low-tech devices, but is compatible with more advanced technologies.

In the ThreeBallot Voting System voters mark three identical blank ballots, casting each of them. To vote for a candidate the voter must select that candidate on two of the three ballots. To vote against a candidate (the equivalent of leaving a ballot blank in other systems) the voter must select that candidate on exactly one ballot.

No candidate can be left blank in the ThreeBallot Voting System, and no candidate can be selected on all three ballots.

At the end of the election, all ballots are published. Each ballot has a unique identifier. Each voter may verify that his votes were counted by searching for the identifier on his receipt amongst the published ballots. However, because the voter selects which of his ballots he receives as a receipt, he can arrange for his receipt to bear any combination of markings. Thus voters cannot prove to another party who they voted for, eliminating vote-selling, coercion, etc. Rivest discusses other benefits and flaws in his paper.^[1]

A field test has found ThreeBallot to have significant privacy, security and usability problems.^[2]