(t, N) Threshold-based Digital Watermarking Protocol

With the development of network and communication technology, the digital products transaction becomes more and more frequent. Because the digital products are easy to copy, it brings copyright protection great challenges. During the 1990s, in order to solve the copyright protection of digital products and the control problem of copying digital products, people put forward the Digital Watermarking Technology. At present, the algorithm of insetting and testing Digital Watermarking is mainly related to Digital Watermarking Technology research. Its main purpose is only protecting the rights and interests of the copyright owner and the rights of consumers could not get protection. In order to protect all the lawful rights and interests of both parties, people pay more attention to the research of the Digital Watermarking Protocol.This paper first introduces the theoretical knowledge on the Digital Watermarking and the Cryptography. Secondly, it overviews and analyses the existing three typical digital watermarking protocol (the MW protocol, the DHWM protocol and the Change protocol). And then, it presents an protocol based on (t, n) threshold according to the problems of both sides rights protection and copying tracking existing in the last protocol. In the protocol, before the start of the trading, both parties apply for the digital signature of this trading from the third CA to prove the identity of both trading sides and the trading legitimacy, prevent intermediaries attack. Consumers provide the embedded watermark in digital products and encrypt it, so this protocol may prevent the sellers'frame-up and reputation and protect the rights of consumers. The CA signs the watermarking by the timestamp and clears the transaction of time, so this may prevent the reversible attack effectively. We using Shamir (t, n) threshold to embed watermark and guarantee the robustness of watermark, so it may resist fuzzy attack and expression attack. In the process of trading, the use of RSA public-key cryptosystem to encrypt messages could prevent watermarking information and digital products leaked and ensure the safety of trading. At last, it designs an application of the new protocol and describes in detail how to use the new protocol to trade online.The characteristic of the research is that it combines the threshold password system with digital watermarking technology, and use them in the digital watermark protocol designing. Then a watermark protocol based on (t,n) threshold system is proposed, with the advantages and application of this protocol. Compared with the existing protocol, the robustness of watermark embeded in the digital products improves greatly. It can resist fuzzy attack and protec the interest of both sides in a transaction.