Blockchain voting: Publicly verifiable online voting protocol without trusted tallying authorities

Abstract In organizing elections, a difficult problem is to achieve trust of all voters in the tallying process. Practical elections often lead to recounting of the submitted votes and raise questions about the validity of many submitted votes. There are even situations, when the opposition raises concerns about the validity of the whole election process due to insufficient transparency in the verification of the votes and in tallying. To solve this problem, the present paper proposes a new voting protocol based on the blockchain technology. There are several main advantages of the protocol. It does not rely on a trusted tallying authority. All votes are submitted with complete proofs of validity and are available for public access in an encrypted form. We propose a new encryption mechanism to guarantee that nobody can decrypt the votes, but everyone can verify the validity of the votes as well as the outcome of the tallying process by using the homomorphic property of the encryption. This makes the results of the election publicly verifiable. Our protocol enables all voters to store, verify, and tally all submitted votes which are added to a blockchain database. They allow every voter to rank each candidate by assigning different scores to them, rather than voting for only one candidate. Each vote is encrypted using a new encryption mechanism before submission. For each encrypted score in the vote, proofs are generated and stored. Everyone can use these proofs to verify the correctness and the eligibility of each submission without decrypting the content of the vote. This ensures the validity of the submitted votes in the counting process and at the same time maintains confidentiality. The security and performance analyses included in this paper demonstrate the feasibility of the proposed protocol for implementation in real elections.