Double Voting Problem of Some Anonymous E-Voting Schemes

In 1998, Mu and Varadharajan proposed an anonymous e-voting scheme to be applied in both small-scale and large-scale elections. They claimed that it protects the anonymity of voters and prevents double voting. They also mentioned that if a malicious voter votes more than once, his identity will be discovered by the election authority. In 2003, Lin et al. demonstrated that the scheme fails to resist double voting and further proposed an enhanced scheme to overcome the weakness. Their scheme has received a much of interest by Yang et al. (2004), Hwang et al. (2005), and Rodriguez-Henriquez et al. (2007). They have improved Lin et al.’s scheme to prevent their proposed weaknesses. This paper indicates that in these anonymous e-voting schemes (started from Lin et al.’s scheme), a valid voter in cooperation with another valid voter can successfully vote more than once. It is also demonstrated that the scheme is unable to recognize a malicious voter who has double voted.