Construction of Highly Reliable Electronic Election Systems

为了在信息技术高度发达的环境下建设民主社会，我们研究了不受现有系统限制的高度可靠的电子选举系统的建设。首先，我们从密码原语的安全性退化的角度重新考虑了可公开验证的投票方案中的隐私问题，并提出了一种构造可公开验证的投票方案的方法，即使在这种安全性退化之后，也能保护用户的隐私。其次，我们关注了投票的时机，并讨论了重新投票对减少贿选和胁迫威胁的作用。最后，我们讨论了选民检查自己的选票的正确性的方法。

For the construction of a democratic society in the highly-developed IT environment, we have examined the construction of highly reliable electronic election systems which do not contain restrictions imposed in the present systems. At first, we have reconsidered privacy problem in publicly verifiable voting schemes from the viewpoint of security degradation of cryptographic primitives and proposed a method to construct publicly verifiable voting schemes protecting user's privacy even after such security degradation. Secondly, we have paid attention to the timing of voting and discussed the effect of re-voting for decreasing the threat of vote-buying and coercion. At last, we have discussed methods for voters to check the correctness of their votes.