We study ballot independence for election schemes. First, we formally define ballot independence as a cryptographic game and prove that ballot secrecy implies ballot independence. Secondly, we introduce a notion of controlled malleability and prove that it is sufficient for ballot independence. We also prove that non-malleable ballots are sufficient for ballot independence. Thirdly, we prove that ballot independence is sufficient for ballot secrecy in a special case. Our results show that ballot independence is necessary in election schemes satisfying ballot secrecy. Furthermore, our sufficient conditions enable simpler proofs of ballot secrecy.
@TechReport{2014-ballot-independence-for-election-schemes, author = "Ben Smyth and David Bernhard", title = "{Ballot secrecy and ballot independence: definitions and relations}", year = "2014", number = "2013/235", institution = "Cryptology ePrint Archive", }