本論文提出了一種基於區塊鏈的對稱式金鑰直接式數位簽章協定。類似於非對稱式金鑰直接式數位簽章協定，用於簽名的對稱式金鑰可以公開來進行簽章驗證，惡意攻擊者不能使用被公開的金鑰來生成偽造簽章。提出的協定滿足數位簽章協定的安全要求。此外，由於使用了區塊鏈機制，因此提出的協定提供了前向安全性(Forward Secrecy)以及能夠支持強匿名性(Strong Anonymity)。
在提出的基於區塊鏈的對稱式金鑰直接式數位簽章協定的基礎上，本論文進一步提出了基於區塊鏈的匿名公開投票系統。這是一個點對點的投票系統，只有投票發起者和投票者參與這個系統。沒有中央伺服器的幫助來進行計票，投票發起者和投票者可以自己完成整個公開投票的程序，其滿足公開投票系統的安全要求。

This thesis proposes a symmetric-key direct digital signature scheme using blockchain technique. Similar to the asymmetric-key direct digital signature scheme, the symmetric key for the signature can be published for verification, and malicious attackers cannot use the published key to generate fake signatures. The proposed scheme satisfies the security requirements of a digital signature scheme. In addition, it provides the forward secrecy and the strong anonymity.
Based on the proposed blockchain-based symmetric-key direct digital signature scheme, this thesis further presents the blockchain-based anonymous public voting system. It is a peer-to-peer voting system: only the initiator and the voters involve in the scheme. Without a central server to count the votes, the initiator and voters can complete the entire public voting process, which satisfies the security requirements of a public voting system.

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