Watermarking Protocol Based On The Semi-trusted Third Party And Its Application

In this paper, we study the problems in customer's right protection and copy tracing fields by applying the theories and techniques of modern cryptography, and present a watermarking protocol based on the semi-trusted third party (WPSTTP). In this protocol, the seller cooperates with the buyer in watermark embedding, so it's fair to the buyer. And the protocol ensures the fingerprint watermark to be private. According to this protocol, the buyer has responsibility for any copy of the multimedia product he has bought; the third party only takes part in the dispute resolution, and he neither knows the information in transaction stage nor the watermark in dispute resolution phase. So the profits of the buyer and seller are protected. All the information at each stage of the protocol is encrypted. Security analysis is also made in this paper, which shows that the protocol meets the requirements of watermark security, fairness, correlation between fingerprint and the entity, private fingerprint, etc.According to the design and security analysis of WPSTTP,we also make the general analysis and designs of the multimedia transaction system based on WPSTTP, and give the basic implementation frame. At the same time, the experiment is done to test the encrypt-security solution. And a new solution to reduce the interactive times is also made.