Research On Relational Data Digital Watermarking Technology

Digital watermark technique is a method that some secret information is embedded into the data to achieve data security without affecting the normal use of the data.And the secret information is difficult to detect and erase.Originally,digital watermark technique is mainly used in image,audio,video and other multimedia data.However,with the widespread use of relational data,its copyright protection has attracted people's attention.Therefore,researchers hope to be able to solve this problem via using digital watermark technique.However,there are still many problems in the existing digital watermarking technology for relational data:(1)most of those watermarking schemes for relational data have limitation on usage times of watermark.In other words,watermark can be used to claim copyright only once due to the exposure of the key and other secret parameters during the watermark detection process.And the watermark in the data may be modified,forged or even removed by the wrongdoers.(2)Traditional digital watermarking technique for relational data will cause permanent distortion of data.Reversible watermarking technique for relational data cannot only claim the copyright of data,but also recover the original data from the watermarked copy.However,existing reversible watermarking schemes for relational data cannot control the extent of data recovery.Aiming at the problem 1,a multi-verifiable reversible watermarking scheme for relational data is proposed in this thesis.Watermark embedding algorithm,watermark detection algorithm and data recovery algorithm are designed.The watermark detection process is controlled by relevant parameters to achieve multiple verification.Difference expansion is used to achieve watermark reversibility.Aiming at the problem 2,a graded reversible watermarking scheme for relational data is proposed in the thesis.Data quality grade is defined to depict the impact of watermark embedding on the usability of data.Watermark embedding,grade detection,watermark detection and grade enhancement algorithms are designed to achieve graded reversibility of watermark.Before distributing the data,the data owner can predefine several data quality grades,then embed the watermark into data partitions.If data users are not satisfied with the usability of data,they can require or purchase relevant keys from the owner to upgrade the data quality grade.The watermark in relational data with any data quality grade is sufficient to prove the copyright.Experiments on algorithms and watermark showed that both schemes are feasible and robust.