臺灣博碩士論文加值系統

　　代理簽章是數位簽章的一種變形。自從Mambo等人在一九九六年提出代理簽章這個概念後，這種簽章的方法應用在移交權力的地方是越來越有用了。例如一個經理出國時可以把他的簽章的相關權力指派給他的秘書。如此一來，他的秘書就可以代替那位經理在他出國的這個時間來幫他進行簽章的動作。
　　但是，目前我們所知道的代理簽章系統都沒有前向式的安全(forward-secure)機制，這樣會使得這類的簽章系統在私鑰被偷後變得非常危險。在我們的論文中，我們提出了一種具有前向式安全機制的代理簽章系統。除此之外，我們將使得不只原來簽章的人有前向式安全的機制來移交他的權力，並且使得代理的人也有前向式的安全機制。我們的系統除了可以降低私鑰被偷的損害，並可以清楚地指出是那位代理人在何時產生該簽章。

　　Proxy signature schemes are the variation of digital signature schemes. Since Mambo et al. proposed the concept of the proxy signature scheme in 1996; it is useful for people to delegate their own power to other party. If a manger delegates his rights to his secretaries while he traveling outside, the secretaries can sign the message on behalf of the manger.
　　As we know, the proxy signature schemes have been proposed before have no forward-secure ability. So, those schemes are dangerous while the secret key exposure. In this thesis, we proposed a proxy signature scheme which has the forward-secure ability. And we not only let the proxy signers have forward-secure but also the original signer has the ability of forward-secure.
In this way, our scheme can prevent the key exposure problem. Besides, our scheme can easily identify who generate the signature in what time period.

Chapter1 Introduction 1
1.1 Introduction 1
1.2 Research Motivates 3
1.3 Our Results 4
1.4 Organization of this thesis 5
Chapter 2 Related Works 6
2.1 Asymmetric Cryptosystem 6
2.2 Digital signature schemes 8
2.2.1 RSA digital signature scheme 8
2.2.2 GQ digital signature scheme 9
2.3 Forward Secure Digital Signature 12
2.4 Proxy Signature 15
2.4.2 Mambo et al.’s proxy signature scheme 17
Chapter 3 Threshold Proxy Signature based on RSA 20
3.1 Introduction 20
3.2 Review of the Hwang’s Scheme 21
3.2.1 The Proxy Sharing Phase 22
3.2.2 The Proxy Signature Issuing Phase 22
3.2.3 The Proxy Signature Verification Phase 23
3.3 Wang et al’s comments [29] on HLL-scheme 23
3.4 Our additional comments on Hwang’s scheme 24
3.4.1 Similar to RSA Reblocking problem 24
3.4.2 Security weakness 25
3.5 Our modify scheme 25
3.6 Conclusion 26
Chapter 4 Our proposed scheme 27
4.1 Introduction 27
4.2 Definitions 28
4.3 Our Algorithm 31
Chapter 5 System analysis 38
5.1 Security 38
5.1.1 Corrupted Attack 1st test 39
5.1.2 Corrupted Attack 2nd test 39
5.1.3 Advanced to Analyze our scheme 39
5.2 Satisfying the Requirements of Proxy Signature 40
5.3 Limitation of our scheme 41
Chapter6 Conclusion and Further work 43
Reference 44

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