臺灣博碩士論文加值系統

學者Simmons在1983年首先提出了潛隱通道的概念。之後，許多關於潛隱通道之數位簽章系統的論文也相繼地被提出。到目前為止，具潛隱通道之數位簽章系統只能隱藏固定的訊息，在簽章產生後，隱藏的訊息也隨之固定下來。此外，傳送者還必須將簽章私鑰與潛隱接收者共享。學者Chaum和 Antwerpen在1989年提出了不可否認的數位簽章系統。之後，學者Chaum也提出了零知識不可否認之數位簽章系統。可轉換不可否認之數位簽章系統允許將不可否認之數位簽章轉換一般的數位簽章。 而 (t,n) 門檻式系統方式將機密分享給n個使用者，使得其中只要有t個或者更多的使用者合作即可解開該機密。
本篇論文的目的如下：
1.將潛隱通道整合在不可否認之數位簽章內：使不可否認之數位簽章可 以 重覆地隱藏訊息。此外，簽章者不須將任何的私鑰與潛隱接收者分享。
2.結合潛隱通道和可轉換不可否認之數位簽章系統的概念：提出一個可將潛隱通道隱藏在可轉換不可否認之數位簽章中的新系統。
3.結合潛隱通道和門檻式的概念：提出了一個可將潛隱訊息傳送給一群潛隱接收者的門檻式潛隱通道。 群體內需要t個或更多人合作才能解出潛隱訊息。此外，在此系統中，潛隱訊息的正確性可以被驗證。

Simmons first proposed the concept of subliminal channel in 1983. Since then, many subliminal channels based on digital signatures are proposed. Up to now, only a fixed number of subliminal messages can be hidden in a digital signature and the content of the subliminal messages cannot be changed after the signature is generated. Moreover, the sender has to share a secret key with the subliminal receivers. Chaum and Antwerpen, in 1989, proposed the concept of the undeniable signature which cannot be verified without the signer’s cooperation. Later, Chaum also proposed a zero-knowledge undeniable signature scheme. A convertible undeniable signature is an undeniable signature and can be converted to a general digital signature. A (t,n) threshold scheme allows a secret to be shared among n users so that only t or more users can reconstruct the secret.
The aims of this Master thesis are as follows.
1. Integrate subliminal channels with an undeniable signature：A undeniable signature can be used to hide subliminal messages repeatedly. Moreover, the sender does not need to share any secret key with the subliminal receivers.
2. Combine subliminal channels with a convertible undeniable signature：We are going to propose a new scheme which can embed subliminal channels into a convertible undeniable signature scheme.
3. Combine subliminal channels with threshold system： We are going to propose the first threshold subliminal channel which can convey a subliminal message to a group of users. Deriving the subliminal message relies on the cooperation of t or more users in the group. Moreover, the validation of the subliminal message can be verified in the scheme.

中文摘要…………………………………………………………………….1
Abstact…………………………………………………………………… .2
誌謝………………………………………………………………………….4
目次……………………………………………………………………….…4
圖表目錄…………………………………………………………………….6
第一章 緒論……………………………………………………………….8
1.1 研究背景………………………………………………………...8
1.2 研究動機與目的………………………………………………….8
1.3 章節概要………………………………………………………….9
第二章 數位簽章系統………………………………………………....10
2.1 數位簽章系統之簡介………………………………………….....10
2.2 不可否認之數位簽章系統之簡介…………………………...13 2.3 可轉換不可否認之數位簽章系統之簡介………………….......17
2.4 門檻式數位簽章系統之簡介………………………………….21
第三章 具潛隱通道之數位簽章系統之簡介………………….........24
3.1 潛隱通道技術………………………………………………….24
3.2 具潛隱通道之數位簽章系統之回顧與現況………………...25
第四章 具潛隱通道之數位簽章系統……………………….….......33
4.1 具可重覆使用潛隱通道之不可否認之數位簽章統………....33
4.1.1 系統架構……………………………………….……….33
4.1.2 安全度分析………………………………………….….36
4.1.3 討論……….…………………………………………….38
4.2 具潛隱通道之可轉換不可否認之數位簽章系統…...……….39
4.2.1 系統架構………………………………………....……39
4.2.2 安全度分析…………………………….………….……42
4.2.3 討論……………………………….……………….……43
4.3具門檻式潛隱通道之數位簽章系統…………………….….….44
4.3.1 系統架構………………………………………….…….46
4.3.2 安全度分析………………………….………………….48
4.3.3 討論…………………………….………………….……49
第五章 結論與未來研究方向……………………………………......50
參考文獻……………………………………………………………………51

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