Coercion-Resistant Electronic Elections with Write-In Candidates

It is often argued in the e-voting community that in the presence of write-in candidates, forced abstention attacks are always possible. Therefore, write-in candidates are often excluded in existing definitions of coercion-resistance arguing that those definitions cannot be achieved by write-in supporting schemes. This is only true if the tally is made public directly. Coercion-resistance may well be achieved if only a fuzzy version of the tally is published. This paper provides a formalization of fuzzy tally representations which enables definitions for coercion-resistance to take into account write-in candidates without being weakened. We also show how the cryptographic voting scheme Bingo Voting can be applied to write-in candidates with respect to this formalization, providing what we believe to be the first evoting scheme that prevents forced abstention while allowing for write-in candidates. We then give a general construction of coercion-resistant schemes that provide a verifiable fuzzy tally representation from mix-based and homomorphic election schemes with trusted authority.