CaIV: Cast-as-Intended Verifiability in Blockchain-based Voting

Democracy in the digital age has attracted a lot of public attention in recent years. However, bringing the human right of secrecy in voting to electronic systems is difficult. Properties, such as the possibility of verifying universally that any vote counted was indeed carrying the decision made by a voter, are often conflicting and a trade-off must be found. This paper proposes a blockchain-based electronic voting system providing explicitly cast-as-intended verifiability. By using a non-interactive zero-knowledge proof of knowledge any voter can verify that his or her encrypted vote represents the decision voted for while maintaining at the same time the secrecy of the ballot. In addition, any required cryptographic material can be generated in linear time with respect to the number of voters, making the system suitable for large scale elections, thus scalable.