數位浮水印是近年來保護個人數位電子資料所有權中最受歡迎的一項技術，數位浮水印是利用嵌入個人資訊至所購買的商品中來達到一個所有權利的聲明。藉由數位浮水印，擁有者可以向法院或是公正單位來證明對商品的所有權與合法的擁有者。目前對於數位浮水印的發展已經邁入了較成熟的階段，演化至今，數位浮水印機制已經成為用來保護使用者所有權與智慧財產權的一個影像處理技術。伴隨著數位浮水印技術發展，擁有者的聲音或是數位影像產品都包含擁有者的版權聲明且可以得到一個好的保護。
在另一方面，數位浮水印也漸漸開始有了新的一些攻擊方式，像是中間人攻擊、移花接木攻擊等，都是危害到數位浮水印的保護機制。此外對於買賣雙方的隱私保護與紛爭解決則是同樣沒有一個良好的解決方式。雖然目前有許多買賣雙方數位浮水印協定機制，但是還是無法有效的解決上述所提及的問題，且能夠有一個良好的解決方案。有鑑於此，我們提出了一個新的買賣雙方數位浮水印機制，一方面可以抵擋上述所提及的問題與攻擊，且另一方面也可以提供買家一個完整的隱私保護與爭議解決方法，同時也結合了數位簽章與密碼學來讓買家能夠對與本身購買的商品可以有好的擁有權保護與交易匿名性功能，讓使用者能夠擁有一個安全智慧財產權保護的電子商務環境。

Digital watermarking is one of the most popular technologies for protecting the ownerships of digital contents or products. By embedding digital watermarks into digital contents, the owners of the contents can convince the judge or the trusted third party of their ownership of the contents. However, some attacks, such as the binding attacks and the men-in-the-middle attacks, are threatening the security of the watermarking mechanisms. Moreover, that the privacy of content buyers is not fully protected or the dispute between the buyers and the sellers cannot be fairly resolved also reduce the quality of the services. Although several buyer-seller watermarking protocols have been introduced in the literature, none can cope with all of the above problems. In this thesis, we will propose a novel buyer-seller watermarking protocol that can resolve the dispute between the buyers and the sellers fairly. Furthermore, not only is the proposed protocol immune to all of the known attacks, but it is truly buyer anonymous as well.

Table of Contents
CHAPTER 1 INTRODUCTION....................................1
CHAPTER 2 PRELIMINARY.....................................6
2.1 WATERMARK EMBEDDING...........................6
2.2 PRIVACY HOMOMORPHISM..........................8
2.3 WATERMARK DETECTION/EXTRACTION................8
CHAPTER 3 RELATED WORKS..................................13
3.1 REVIEW OF MEMON AND WONG’S SCHEME...........13
3.1.1 The watermarking generation protocol.......14
3.1.2 The watermark insertion protocol...........15
3.1.3 The copyright violation detection protocol 16
3.1.4 The dispute resolution protocol............16
3.2 REVIEW OF LEI’S SCHEME.......................16
3.2.1 The registration Protocol..................18
3.2.2 Watermarking protocol......................18
3.2.3 Identification and Arbitration protocol....20
3.3 REVIEW OF CHANG'S SCHEME......................22
3.3.1 Detection of copyright violation...........23
3.3.2 Dispute resolution.........................23
CHAPTER 4 THE PROPOSED SCHEME............................25
4.1 THE WATERMARKING PROTOCOL..............26
4.1.1 The watermark generation stage.............26
4.1.2 The watermark insertion stage..............27
4.2 THE BUYER TRACING PROTOCOL.............30
CHAPTER 5 DISCUSSIONS....................................31
CHAPTER 6 CONCLUSIONS....................................34
REFERENCES...............................................35

References
[1] A. Adelsbach and A. Sadeghi, ”Zero-Knowledge Watermark Detection and Proof of Ownership,” LNCS, no. 2137, pp. 273-288, 2001.
[2] C. C. Chang and C. Y. Chung, ”An Enhanced Buyer Seller Watermarking Protocol,” International Conference on Communication Technology Proceedings, vol. 2, pp. 1779-1783, 2003.
[3] C. L. Lei, P. L. Yu, P. L. Tsai, and M. H. Chan, ”An Efficient and Anonymous Buyer-Seller Watermarking Protocol,” IEEE Transactions on Image Processing, vol. 13, no. 12, pp. 1618-1626, 2004.
[4] D. Chaum, ”Untraceable Electronic Mail, Return Address, and Digital Pseudonyms,” Communications of the ACM, vol. 24, no. 2, pp. 84-88, 1981.
[5] D. R. Stinson, Cryptography: Theory and Practice, 1st ed., New York: Chapman & Hall, 1995.
[6] D. Chaum, A. Fiat, and M. Naor, ”Untraceable Electronic Cash,” Advances in Cryptology-CRYPTO’88, LNCS 403, Springer-Verlag, pp. 319-327, 1990.
[7] G. J. Simmons. ”The Prisoner’s Problem and The Subliminal Channel,” Proceedings of Crypto-83, 1984.
[8] K. Kuroda, M. Nishigaki, M. Soga, A. Takubo and I. Nakamura, ”A Digital Watermark using Public-Key Cryptography for Open Algorithm,” Proc. International Conference on Information Technology & Applications, pp. 131-21, 2002.
[9] L. Quian and K. Nahrstedt, ”Watermarking Schemes and Protocols for Protecting Rightful Ownership and Customer’s Rights, ” Journal of Visual Communication and Image Representation, vol. 9, pp. 194-210, 1998.
[10] N. Memon and P. W. Wong, ”A Buyer-Seller Watermarking Protocol,” IEEE Transactions on Image Processing, vol. 10, no. 4, pp. 643-649, 2001.
[11] N. Memon and P. W. Wong, ”Protecting Digital Media Content,” Communications of the ACM, vol. 41, no. 7, pp. 35-43, 1998.
[12] N. Ahituv, Y. Lpid and S. Neumann, ”Processing Encrypted Data,” Communications of the ACM, vol. 30, pp. 777-780, 1987.
[13] P. W. Wong, ”A Public Key Watermark for Image Verification and Authentication,” Int. Conf. Image Processing, vol. 1, pp. 455-459, 1998.
[14] R. L. Rivest, L. Adleman and M. L. Dertouzos, ”On Data Banks and Privacy Homomorphisms, ” Foundations of Secure Computation, Academic Press, pp. 169-179, 1978.
[15] R. L. Rivest, A. Shamir and L. Adleman, ”A Method for Obtaining Digital Signatures and Public Key Cryptosystems,” Communications of ACM, vol. 21, pp. 120-126, 1978.
[16] S. Craver, ”Zero knowledge watermark detection,” LNCS, vol. 1768, pp. 101-66, 1999.
[17] Z. Liu, X. Li, and Z. Dong, ”Multimedia Authentication with Sensor-based Watermarking,” International Multimedia Conference Proceeding of the multimedia and security workshop, ACM-Press, pp. 155-109, 2004.