  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 masked unique prime. 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.
