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(Ed.)
A boardroom election is an election with a small number of voters
carried out with public communications.
We present BVOT, a self-tallying boardroom voting protocol with ballot secrecy,
fairness (no tally information is available before the polls close), and
dispute-freeness (voters can observe that all voters correctly followed the protocol).
BVOT works by using a multiparty threshold homomorphic encryption system in
which each candidate is associated with a set of masked primes.
Each voter engages in an oblivious transfer with an untrusted distributor:
the voter selects the index of a prime associated with a candidate and receives the selected prime
in masked form. The voter then casts their vote by encrypting their masked prime
and broadcasting it to everyone.
The distributor does not learn the voter's choice, and no one learns
the mapping between primes and candidates until the audit phase.
By hiding the mapping between primes and candidates, BVOT provides voters
with insufficient information to carry out effective cheating.
The threshold feature prevents anyone from computing any partial
tally---until everyone has voted.
Multiplying all votes, their decryption shares, and the unmasking factor
yields a product of the primes each raised to the number of votes received.
In contrast to some existing boardroom voting protocols,
BVOT does not rely on any zero-knowledge proof;
instead, it uses oblivious transfer to assure ballot secrecy and correct vote casting.
Also, BVOT can handle multiple candidates in one election.
BVOT prevents cheating by hiding crucial information:
an attempt to increase the tally of one candidate
might increase the tally of another candidate.
After all votes are cast, any party can tally the votes.
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