Theories And Methods Research On Reversible Data Hiding For 3D Mesh Models

Digital multimedia has become an important carrier for people to share and transfer information.But in recent years,lots of privacy leak cases have been reported frequent-ly,more and more people begin to care about the information security problems.Infor-mation hiding provides an effective technology to solve the problem of digital multime-dia information security.Compared to the traditional cryptography,information hiding method can not only protect the content of messages,but also carry on the protection to transfer behavior,it realizes the security transformation for important information in silence.Reversible data hiding is an important branch of information hiding,which re-quires both the embedded information can be accurately extracted,and the carrier can be restored losslessly.The reversibility can be applied to some sensitive scenarios,such as medical treatment,military application and law trial.In these scenarios,even if a s-mall error on the original multimedia,will cause big change for the result.In recent years,a lot of reversible data hiding method for digital images have been proposed in order to protect the authenticity and completeness of images.However,for other digital multimedia types,related research is still at the first stage.With the popularization and application of 3D related technology,3D models are widely used in various fields.The medical industry uses them to produce human organ models.The field of military uses them to build 3D geological models.The field of science uses them to introduce the structure of the compounds.The field of entertain-ment uses them to design characters.The manufacturing industry uses them to print the real components.Even in the field of electronic commerce,3D models are used to show online goods.That is to say,after image,audio and video,the 3D model as the fourth generation of digital multimedia type,has appeared in all aspects of human life.In the complicated and sensitive application scenarios,even if only a small change on the 3D model will cause it no longer meet the demand of use.Therefore,reversible data hiding method based on 3D models has significant theoretical and practical values,for effectively protect the authenticity and completeness of 3D models.The dissertation explores reversible data hiding methods for 3D mesh models,which is the most common type of 3D models.The main contributions and innova-tions are as follows:1.Proposed a kind of 3D reversible data hiding algorithm based on objective quality evaluationBased on the characteristics of 3D models,this dissertation proposes a new predic-tion method to construct the prediction error with steeper histogram.Considering the vertex attribution and the correlation between prediction errors,every three prediction errors are combined to construct the prediction-error unit with smaller entropy.By defining the distortion matrix suitable for 3D model,and introducing the mapping function,recursive code construction can be applied to realize the optimal three-dimensional prediction-error histogram modification.The experi-mental results show that the proposed algorithm earns an average of 10dB at the same embedding capacity,compared to the existing algorithms.Meanwhile,the proposed algorithm is flexible,in which the prediction and embedding procedure can be kept several rounds in order to further improve the embedding capacity under the limit of distortion.2.Proposed a kind of 3D reversible data hiding algorithm considering human visual systemThe existing 3D reversible data hiding methods are considering the objective qual-ity assessment.In practice,the objective indicators cannot be exactly the same as human visual perception.This dissertation proposed a kind of 3D reversible data hiding algorithm considering the human system.Through analyzing the charac-teristics of 3D model distortion,we use discrete Laplacian of gaussian curvature to define the local complexity for each vertex.With sorting algorithm,the ver-tices with good masking effect are selected in priority for data embedding.In this way,the human visual perception caused by 3D model distortion can be re-duced.At the same time,by introducing the double-layered prediction scheme,the reversibility can be realized.The experimental results show that the proposed algorithm can effectively reduce the human visual distortion under the same em-bedding capacity.3.Proposed a kind of reversible data hiding algorithm in encrypted domainThis dissertation expands 3D reversible data hiding from plaintext domain into ciphertext domain,which can not only protect the content of 3D models,but also manage the encrypted models in order to realize the authentication and integrity authentication.At the embedding process,the owner of 3D model firstly map each vertex coordinates into the integer,and encrypt them with stream cipher.Then the data hider calculates "the embedded set" on encrypted mesh model,and carry on xor operation for least significant bit of the decimal coordinates in order to embed watermark.At the extraction process,the legal users firstly decrypt the encrypted mesh model,then extract the embedded data according to the spatial correlation of 3D mesh model and restore the original 3D mesh model.The dissertation selects two public 3D mesh model database for experiments,the experiment results showed that the average error rate of extracting data is only 4.22%,if the introduction of error correction coding,it can reduce the error rate to 0.At the same time,the proposed algorithm has the characteristics of high embedding capacity and low computation complexity,and the directly decrypted 3D model have good visual quality.