應用密碼技術於可驗證之無記名投票

Abstract

處在這高度資訊化的社會,幾乎事事都要倚賴電腦,而隨著電腦網路的普遍 化,人們一些群體活動(例如群體決策)也漸漸借助電腦來完成。而通常大 家在意見溝通後,即以投票進行表決。因此,運用密碼學的技術來設計一安 全可靠之電子投票協定便成為重要課題。目前,相關研究並非很完善,我們 將嘗試提出一新的解法,其能保留各家精華,並能有所突破。在假設電子投 票系統不存在"公正第三者"的情況下,我們的方法符合下列要求: (1)只有 合法投票者才能投票,且一人一票。 (2)僅投票者本身知道其投票策略,他 人(含計票中心)不易從網路中竊取或聯合攻擊得知。 (3)在投票截止前, 投票者可更改其選票。 (4)開票後,投票者可檢視其選票是否被正確納入 計票。 其中,(3)、(4)兩點為現行人工計票系統無法達成之功能。 Recent development of computer applications has been moving toward supporting group, instead of individual, activities. Since group decisions are usually accomplished through voting, how to design reliable protocols for anonymous and verifiable voting is an important research topic. Current protocols in literatures for anonymous voting appear to have some disadvantages. Either the protocol is not efficient enough for practical applications, or the protocol cannot sustain cooperative attacks or can be cheated by a dishonest government. So,we try to develop new and better protocols under there exists no honest government assumption. Generally speaking, our protocols satisfy the following properties: (1) Only legitimate voter may cast a valid vote and each legitimate voter may cast only one valid vote. (2) No one but the voter knows which voting strategy the voter adopts. (3) Each legitimate voter may change his/her mind within a given period of time. (4) Each voter may check that his/her vote has been counted.