# PVPBC: Privacy and Verifiability Preserving E-Voting Based on Permissioned Blockchain
## 2 Related Work  
E-voting is attracting increasing research attention. The aim of this research has been to preserve the key attributes of e-voting which are privacy, integrity, transparency, and E2E verifiability. From the protocol point of view, preserving vote privacy is challenging when e-voting systems are being designed. Several mechanisms have been adopted in the literature to guarantee privacy in e-voting systems. One mechanism is to use blind signature schemes [8]. The distinguishing feature of these schemes is that the voter receives a token which includes a blind signature from the administrator as an indication of the voter's eligibility to vote. In response to this, the voter should send their vote anonymously along with the signed token as a proof of eligibility. An alternative approach is to use homomorphic encryption [9]. In this approach, the voter encrypts their vote. After that, the administrator determines the encrypted tally from the encrypted votes by making use of the encryption algorithm's homomorphic properties. Randomness, which is achieved using mix-nets, is also an exploited mechanism to preserve privacy by mixing up votes so that the connection between voters and their ballot is obscured [10]. Homomorphic encryption is the foundational principle for a number of e-voting systems. In the system proposed in [11], the voter can encrypt their vote and generate a proof of validity which does not require interaction--this is referred to as a zero-knowledge proof- by making use of an El-Gamal scheme and a set of private and public keys that are shared between parties. A coalition of honest authorities can check the proofs from the voters and then combine all correct encrypted votes in order to decrypt them utilising the proofs. Even though most of the security requirements are fulfilled, the complexity of the proofs as well as the form of the votes affects the scalability of the system. Several proposals for E2E-verifiable voting systems, which employ common verifiability techniques to support the integrity, and thus the credibility of the election, have been introduced. Selected examples include Pret a Voter [12], Wombat [13], Scantegrity II [14], Helios [11], Belenios [15], Civitas [16], and the Selene protocol [7]. These techniques are suitable for either paper voting or electronic voting. Recent verifiability techniques target remote voting from the voter's device. The Benaloh Challenge, which is discussed in [17], is a typical mechanism to confirm that a vote is cast according to the voter's intent where a cut-and-choose method is applied to ensure that the vote is accurately constructed. After creating the vote and encrypting it, the voter has two options, either to cast the vote or to audit it. The auditing process involves the disclosure of the vote, without casting it, and offers proof that the vote was accurately constructed. The voter is able to carry out vote auditing several times before submitting an un-audited vote. This action is achieved by using one of the following algorithms, the Helios, Belenios, Civitas or the Wombat algorithm. Pretty Good Democracy [18] is a verifiable e-voting system which makes use of a Code-Vote approach as a way to obtain individual verifiability. A code sheet is given to the voter in this approach, which contains a voting code for each candidate, as well as a return code. These codes are delivered to the voter using a private channel such as the post. During the voting phase, the voter casts their vote by submitting the code of their candidates. Using the return code, the voter extracts verification that the vote has been correctly received. This is possible because only the election system has knowledge of the voting codes and the return codes. In recent years, several Internet voting systems have been proposed that either use DL technology or have been launched as DL-based systems [19; 20; 21; 22].