代理簽章的架構主要是由原始簽章者授權給代理簽章者，代替原始簽章者去簽署文件；於現實世界中，衍生保護代理簽章者的需求，因此匿名的代理簽章架構主要是為了保護代理簽章者的隱私權而產生。最早的代理簽章觀念，於1996年由日本學者所提出，陸續有許多相關的論文相繼產生。於2002年，Sum 及Wei提出了一套實用的代理簽章架構，採用匿名憑證中心的觀念，核發匿名憑證給代理簽章者，但該架構被證實並沒有符合不可偽造的特性。因此，我們期望可以發展出一套的匿名代理簽章架構，符合匿名簽章應包含的特性及實用性。為了達成該需求，將導入同時簽章法(Concurrent signatures)的特性於匿名簽章申請階段，並證明該架構的安全性。

Proxy signature schemes with anonymous proxy signers are called anonymous proxy signature schemes.  Anonymous proxy signature schemes are used to protect proxy signers’ privacy.  Among the proposed anonymous proxy signature schemes, Sum and Wei’s scheme is more practical than the other proposed scheme.  However, their scheme does not satisfy strong unforgeability.  Here, a new practical anonymous proxy signature scheme is first proposed with the help of concurrent signature schemes.  In the new scheme, the anonymous names of proxy signers keep secret before use to protect proxy signers’ privacy.

Chapter 1 Introduction	I
Chapter 2 Review of asymmetric concurrent signature algorithms	5
2.1.	Two promises of signatures schemes	5
2.2.	Asymmetric concurrent signature schemes	6
2.3.	Asymmetric Concurrent signature protocol	9
Chapter 3 Our scheme with trusted alias issuing authority	11
3.1	Underlying algorithms	11
3.2	Our scheme with trusted authority	12
3.3	Security analysis	16
Chapter 4 Our scheme without trusted alias issuing authority	20
4.1.	Our scheme without trusted alias issuing authority	20
4.2.	Security analysis	24
Chapter 5 Discussions and Conclusions	27
References	28
Appendix-A practical anonymous proxy signature scheme with trusted alias issuing authority            30

[1]	Chen, L., Kudla, C., and Paterson, K. G., “Concurrent signatures,” Eurocrypt ’04, LNCS 3027, New York: Spriger-Verlag, pp. 287-305, 2004.
[2]	Hwang, Shin-Jia and Shi, Chi-Hwai, “A proxy signature scheme without using one-way hash functions,” 2000 International computer symposium, Chiayi, Taiwan, R.O.C., Dec. 6-8, pp. 60-64, 2000.
[3]	Hwang, Shin-Jia and Shi, Chi-Hwai, “The specifiable proxy signature,” National computer symposium 1999, Vol. 1334, Taiwan, pp. 190-197, December 1999.
[4]	Kim, S., Park, S., and Won, D., “Proxy signatures, revisited,” ICICS ’97, LNCS 1334, New York: Springer, Berlin, pp. 223-232, 1997.
[5]	Khanh Nguyen, “Asymmetric concurrent signatures,” Information and Communications Security Conference, ICICS 2005, Lecture Notes in Computer Science 3783, pp.181-193, Springer-Verlag, 2005.
[6]	Li, Li-Hua, Tzeng, Shiang-Feng, and Hwang, Min-Shiang, “Generalization of proxy signature-based on discrete logarithms,” Computers & Security, Vol. 22, No. 3, pp. 245-255, 2003.
[7]	Lee, Narn-Yih, Hwang, Tzonelih, and Wang, Chin Hung, “On Zhang’s nonrepudiable proxy signature schemes,” Third Australasian Conference, ACISP ’98, pp. 415-422, 1998.
[8]	Lee, Narn-Yih and Lee, Ming-Feng, “The security of a strong proxy signature scheme with proxy signer privacy protection,” Applied Mathematics and Computation, Vol. 161, pp. 807-812, 2005.
[9]	MAMBO, Masahiro, USUDA Keisuke, and OKAMOTO, Eiji, “Proxy signatures: Delegation of the power to sign message,” IEICE. Trans. Fundamentals, E79-A, 9, pp. 1338-1354, 1996.
[10]	MAMBO, Masahiro, USUDA, Keisuke, and OKAMOTO, Eiji, “Proxy signatures for delegation signing operation,“ Proc. 3nd ACM Conference on Computer and Communication Security, pp. 48-57, 1996.
[11]	Mehta, M. and Harn L. “Efficient one-time proxy signatures,” IEE Proc.-Commun., Vol. 152, No. 2, April 2005
[12]	Shum, K. and Wei, Victor K., “A strong proxy signature scheme with proxy signer privacy protection,” Proceedings of the IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WETICE’02), pp. 55-56, 2002.
[13]	Schnorr, C.P., “Efficient identification and signatures for smart cards,” Advances in Cryptology - CRYPTO 1989, Lecture Notes in Computer Science 435, pp.239-252, Springer-Verlag, 1990.
[14]	Wang, Guilin, Bao, Feng, and Zhou, Jianying, “The Fairness of Perfect Concurrent Signatures,” ICICS 06, LNCS 4307, New York: Spriger- Verlag, pp. 435-451, 2006.