臺灣博碩士論文加值系統

過去關於合約簽署協定的論文中並沒有討論到密袐保護的特性。然而對於某些商業考量，合約的內容及合約簽章是須要被保護的。若是合約內容或是簽章遭到洩漏，那麼參與合約簽署者就可能會因為別人的濫用而遭受到巨大的損失。在1977年Franklin和Reiter首先提出了保護交換秘密來避免可信任第三者濫用的公平交換協定。但是這樣的協定總是須要一個線上式半信任第三者介入而且不適用於簽章的交換上。
在這篇論文中我們提出了數個引入離線半信任第三者的公平交換協定，分別可使用於秘密或簽章的交換及合約簽署上。這些協定具有良好的效率，因為第三者只有在協定發生錯誤或參與者在交換的程序上有圖謀不軌的行為發生時才會介入協定中。此外，這些協定提供了秘密保護的特性來避免第三者的濫用。我們結合了多人簽章的技巧來減少儲存容量的要求。這個技巧也使得我們的協定能夠符合傳統書面合約的簽署方式。

The previous proposed contract signing protocols have never discussed the property of secret protection. However, the contracts together with the participants’ signatures are needed to be kept secret for some commercial reasons. If they are disclosed, it may be caused that the participants lose their enormous benefits. The first work to protect exchanged secret from TTP’s misuse was proposed by Franklin and Reiter in 1997. But their scheme only employs an on-line semi-trusted third party (on-line STTP) and is unsuitable for exchanging signatures.
In this thesis, we presented several fair exchange protocols with off-line semi-trusted third party (off-line STTP) for exchange of secrets/signatures or being applied to contract signing. These protocols have high performance because TTP only takes part in the protocol when an error occurs or some party takes malicious behaviors during the exchanging process. The property of secret protection will be developed in the off-line TTP model to avoid the misuse of the participiant parties’ signatures. In addition, we combine the multi-signature scheme into the exchange protocols to reduce the storage requirements. This approach also makes our protocols consist with the usage of traditional paper-based contract signing.

中文摘要 i
ABSTRACT ii
誌謝 iii
目錄 iv
圖目錄 viii
表目錄 ix
第一章 緒論 1
1.1研究動機 1
1.2 研究目的 3
第二章 相關研究 6
2.1 公平交換協定的發展 6
2.2 運用可信任第三者之公平交換 6
2.3運用離線可信任第三者之公平交換 8
2.4 使用半信任第三者之公平交換 11
2.5 合約簽署協定 14
2.6 指定確認者簽章 15
第三章 具袐密保護之公平交換協定 17
3.1 使用之技術概論 17
3.1.1 離線半信任第三者 18
3.1.2 附有驗證特性的單向函數 18
3.1.3基於離散對數之可驗證加密系統 19
3.2 建構具秘密保護之公平交換協定 21
3.3 安全性的問題及特性討論 24
3.3.1 協定的公平性 24
3.3.2 協定中交換秘密的保護 26
第四章 具袐密保護之公平交換協定延伸運用 27
4.1 具袐密保護之簽章公平交換協定 27
4.2 具袐密保護之簽章與秘密的公平交換協定 29
第五章 使用Harn多人簽章技巧之合約簽署協定 31
5.1 Harn多人簽章方法 31
5.1.1 公開金鑰的產生階段 31
5.1.2 多人簽章的產生階段 32
5.1.3 多人簽章的驗證階段 33
5.2 符合傳統合約簽署的協定 33
5.3 具袐密資訊保護之合約簽署協定 36
第六章 使用Schnorr-like多人簽章技巧之合約簽署協定 39
6.1 Schnorr-like之多人簽章技巧 39
6.1.1 公開金鑰的產生階段 39
6.1.2 多人簽章的產生階段 39
6.1.3 多人簽章的驗證階段 40
6.2 符合傳統型式的Schnorr-like的多人簽章合約簽署協定 41
6.3 具有秘密資訊保護的Schnorr-like多人簽章合約簽署協定 42
6.4 安全性的問題及特性討論 44
6.4.1 合約簽署的公平性 44
6.4.2 合約簽署協定中合約內容的保護 45
6.4.3 縮減了對儲存空間的要求 46
6.4.4 對抗偽造攻擊的安全性 46
6.5 合約簽署協定的改進 47
第七章 使用指定確認者多人簽章技巧之合約簽署協定 50
7.1 確認者委任技巧 50
7.1.1 金鑰及參數設定 51
7.1.2 確認者委任建構 51
7.1.3 由確認者與驗證者的委任驗證 51
7.1.4 由委任製作者與驗證者的委任驗證 52
7.2 Schnorr-like多人確認者簽章 54
7.2.1 公開金鑰的產生階段 54
7.2.2 多人簽章的產生階段 54
7.2.3 多人簽章的驗證階段 55
7.3 具簽章保護的指定確認者合約簽署協定 56
第八章 總結與未來研究方向 59
參考文獻 62

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