  This paper presents two approaches of privacy-preserving voting system: Blind
Signature-based Voting (BSV) and Homorphic Encryption Based Voting (HEV). BSV
is simple, stable, and scalable, but requires additional anonymous property in
the communication with the blockchain. HEV simultaneously protects voting
privacy against traffic-analysis attacks, prevents cooperation interruption by
malicious voters with a high probability, but the scalability is limited. We
further apply sampling to mitigate the scalability problem in HEV and simulate
the performance under different voting group size and number of samples.
