KR20090044438A - Method for the joint-creatorship verification using multiple digital watermarking framework - Google Patents

Abstract

In virtual environments, virtual reality data ("VR data") is often co-authored by many producers. Measures should be taken to protect joint ownership and ownership of each participating producer. In the present invention, the joint ownership problem is solved by using a multiple digital watermarking framework (MDWF). The proposed multiple watermarking framework uses 3D secret multiple watermarking technology and a key shared cryptographic protocol to demonstrate joint ownership of VR data produced through collaboration. After the key agreement is made for all secret keys, the multiple watermarking framework inserts an additional 3D secret watermark for joint ownership. Thus, multiple watermarking frameworks can successfully resolve ownership disputes between joint participants. In other words, each participating producer can prove their partial ownership and co-ownership by the multiple watermarking framework. Furthermore, the multiple watermarking framework can solve the collusion problem because a shared secret key (SSK) is produced by each user.

Description

How to prove joint ownership with multiple watermarking frameworks {METHOD FOR THE JOINT-CREATORSHIP VERIFICATION USING MULTIPLE DIGITAL WATERMARKING FRAMEWORK}

1 is a block diagram illustrating a conceptual diagram of a secret key sharing protocol utilizing a trusted third party (TTP).

2 is a block diagram illustrating a conceptual diagram of a secret key sharing protocol using multi-party computing.

3 is a block diagram showing a joint ownership verification method using a multiple watermarking framework according to the present invention.

As an example of FIG. 4 and a mesh simplification attack, the left figure of FIG. 4 is an example model with a mesh representation consisting of 10648 triangles, and the right figure is a model in which a watermark is inserted into the example model. Inserted in blue).

5 is a model diagram after a mesh simplification attack, and illustrates a case in which a mesh representation composed of 5262 triangles is performed by performing a 50% mesh simplification.

FIG. 6 is a model diagram after a mesh simplification attack and illustrates a case where a mesh representation composed of 9569 triangles is performed by performing a 10% mesh simplification.

The present invention relates to a method of joint ownership proof using multiple watermarking frameworks. More specifically, the present invention relates to a joint ownership verification method using a multiple watermarking framework.

With the development and distribution technology of digital contents and communication technology, the creation and distribution of many digital works is increasing and the collaboration in distributed environment is also increasing. However, the development and distribution technology of digital works enables the illegal copying and leakage of digital information, so that information protection technology for digital contents such as corporate information that is regarded as a valuable asset is also being developed [Jang Hang-bae, Lee Ho-shin, "Design and Implementation of Information Security System for Prevention of Design Information Leakage", Korean Society of CAD / CAM Engineers, Vol. 11, No. 5, pp. 327-334, 2006].

In particular, 3D data used in manufacturing enterprise environments are often large volumes and include a variety of expertise to produce, often produced by the collaboration and division of labor of many people. When creating 3D data in collaboration, the issue of ownership of the works of the creators who participated in the collaboration is an important issue. First, all collaborators want to be given ownership of the data they create. Second, all the creators involved in the collaboration want to be recognized for their common ownership of the final product. Third, some creators who participate in the collaboration want to prevent the other owners from ignoring ownership and claiming and selling the entire work.

Until recently, research on watermarking methods for proof of joint ownership has been very small [Cox et al., "Digital Watermarking", Academic Press, ISBN: 1-55860-714-5, 2002; And Arnold et al., "Digital Watermarking and Content Protection", Artech House, ISBN: 1-58053-111-3, 2003.

Guo and his colleagues introduced a method of image watermarking for proof of joint ownership [Guo et al., "Digital Image Watermarking for Ownership Verification Without a Trusted Dealer", in Proceedings of ACM Multimedia 2002, Dec. 2002]. This method inserts / extracts an image watermark through secret key sharing in the absence of a trusted dealer and is a watermarking method characterized in the image. By incorporating each owner's watermark and a joint watermark generated by sharing a private key, full and partial claims can be made. This method, however, can cause problems for several owners to conspire and claim ownership of the entire work.

Zhang and his colleagues proposed a watermarking framework for joint ownership [Zhang et al., "A Novel Watermarking Framework for Joint-Creatorship Protection", Proceedings of Cyberworlds 2005, Singapore, pp. 109-116, Nov. 2005], the copyright holder who participated in the work inserts the watermarking into their own works and makes an electronic signature. The above process is repeated for each step of data modification until the final result is obtained. However, this method may also cause a problem of unity for the entire work, and the operation load may be high because the digital signature protocol requires a complicated operation at each stage of modification.

In the present invention, the joint ownership problem is solved by using a multiple digital watermarking framework (MDWF). The proposed multiple watermarking framework uses 3D secret multiple watermarking technology and a key shared cryptographic protocol to demonstrate joint ownership of VR data produced through collaboration. After the key agreement is made for all secret keys, the multiple watermarking framework inserts an additional 3D secret watermark for joint ownership. Thus, multiple watermarking frameworks can successfully resolve ownership disputes between joint participants. In other words, each participating producer can prove their partial ownership and co-ownership by the multiple watermarking framework. Furthermore, the multiple watermarking framework can solve the collusion problem because a shared secret key (SSk) is produced by each user.

The joint ownership proof method using the multiple digital watermarking framework ("MDWF") according to the present invention is to eliminate the ownership dispute of the creators of 3D data through collaboration and provide a reliable relationship. Prove ownership of the contributions they made in the creation of the entire data created through collaboration, while at the same time demonstrating common ownership of the entire work. Moreover, the proof of ownership of the entire work is made only by everyone involved in the production, which prevents unreasonable proof of ownership due to the conspiracy of some people in the production. MDWF is applied to 3D data generation process and utilizes 3D private watermarking technology and key sharing encryption protocol for secret key sharing.

1. 3D watermarking

1.1 3D Watermarking

Watermarking technologies are classified according to the type of media medium to which they are applied. Currently, image, audio, and video watermarking technologies are mainstream. However, as the use of CAD-based 3D data has increased rapidly and the sales of products using such data in virtual space have increased, problems related to ownership of the company or the owners of such data have arisen. Problems such as illegal copying and distribution of 3D-based data can be prevented by inserting information such as identification of copyright holders into 3D data, and the information inserted for proof of ownership is called a watermark. This information also allows the owner to identify the source of the illegal distribution of data.

Watermark embeddable media types of VRML (Virtual Reality Modeling Language) models can be largely divided into audio samples, texture and background images, and 3D geometric-based data. However, since audio samples, textures, and background images can be easily removed without significant loss of the value of the entire VRML data, most 3D watermarking techniques use 3D geometry-based model data for watermark embedding.

In general, watermarks can be broadly divided into private watermarks and public watermarks. Secret watermarks contain information such as the owner's identity to prove ownership in disputes. To extract such secret watermarks, a secret key must be known only to the person who inserted the watermark.

1.2 3D Secret Watermarking System

There are several methods for embedding secret watermarks in 3D models, including changing meshes, changing phases, and inserting visible patterns. The present invention is not particularly limited to the watermark embedding method. In order to prove the usefulness of the present invention, 3D secret watermarks were inserted by the mesh changing method as an embodiment. For further details on how to change the mesh, please refer to O. Benedens, "Geomery-Based Watermarking of 3D models," IEEE Computer Graphics and Applications ", Special Issue on Image Security (January / February 1999), pp. 46-55.

Specifically, a 3D secret watermarking system using bins presented in this document is used. This method uses a change in the normal distribution to ensure independence in the mesh representation. The watermark insertion and extraction procedure of the 3D watermarking system using bins, which is the basis of MDWF, is as follows.

1.3.1 3D Secret Watermark Insertion Procedure

A watermark is inserted by receiving a mesh representation consisting of triangle patches of 3D model data as input and changing the normal distribution of the mesh surface. In particular, "bin", a set of curved patches, is used to input 1 bit of watermark, and "bin" is selected according to the secret key. The watermark embedding procedure using this method is as follows.

E1. Receive a mesh representation consisting of triangle patches of 3D model data and calculate surface patch normals from the input

E2. Based on each user's secret key, Sk _i , sample the normals of the model to generate each user's own bin

E3. Insert secret watermark W _i by applying secret watermark embedding algorithm

2. Multiple Watermarking Framework

The multi-watermarking framework proposed by the present invention uses a 3D secret multi-watermarking technology and a cryptographic protocol for secret key sharing as a method of proving joint ownership of VR data produced through collaboration. The above-mentioned 3D secret watermarking technique is robust against various phase / geometric attacks such as mesh simplification, and multiple watermark embedding is possible by selecting bins used for watermark embedding. Therefore, in the following, we introduce a secret key sharing method for proof of joint ownership and describe the MDWF based on secret watermarking and secret key sharing methods in detail.

In particular, Guo et al., "Digital Image Watermarking for Ownership Verification Without a Trusted Dealer", in Proceedings of ACM Multimedia 2002, Dec. In the private key sharing protocol introduced by 2002], it is assumed that there is no Trusted Dealer. However, VR data used in a manufacturing enterprise environment is used as a server for VR data registration for security management purposes. It is common to assume the existence of a trusted third party (TTP). Therefore, the present invention proposes a secret key sharing protocol by dividing the case of assuming the presence of TTP and the case of not assuming TTP.

2.1 Secret Key Sharing Protocol

n users O ₁ , O ₂ ,.. , To O _{n the} secret keys Sk ₁ , Sk ₂ ,... , Sk _n is given. The following secret key sharing protocol uses the hash function H.

2.1.1 Secret Key Sharing Protocol Using Trusted Third Party (TTP)

A block diagram showing a conceptual diagram of a secret key sharing protocol utilizing a trusted third party (TTP) is shown in FIG. The specific procedure of the secret key sharing protocol using TTP is as follows.

-User O _i (i = 1,…, n) passes his private key Sk _i to the TTP

-TTP calculates and outputs shared secret key SSk = H (Sk _{1 ·} Sk _{2 ·} … · Sk _n ) for joint ownership proof

2.1.2 Secret Key Sharing Protocol Using Multi-party Computation

A conceptual diagram of a secret key sharing protocol utilizing multi-party computation without assuming TTP is shown in FIG. 2. If TTP is not assumed, the key sharing server assumes that the hash function H used has a homomorphic property that satisfies H (a) H (b) = H (ab) for all inputs a and b. Server: KSS) participates in multi-party calculations.

The user O _i (i = 1,…, n) calculates the hash value H (Sk _i ) for his private key Sk _i and passes it to KSS.

-KSS is based on the received hash value, the shared secret key SSk = H (Sk ₁ Sk ₂ ... Sk _n ) = H (Sk ₁ ) H (Sk ₂ ). Calculate and output H (Sk _n )

2.2 How to insert multiple watermarks

3D data I _T = (I ₁ , I ₂ ,…, I _n ) is n co-producers O ₁ , O ₂ ,. , Generated by a _n O, and each producer _{O i (i = 1, ...} , n) selects a secret key Sk _i required for the secret watermark W _i inserted. Multiple watermark embedding process for the co-ownership credentials for each producer O _i at the same time as proof of ownership of the asset to the entire work I _i I _T is as follows (see Fig. 3)

-Insert the secret watermark W _i using the Watermarking Embedding Algorithm (3DEA) described above by receiving the author's O _i secret key Sk _i for each work I _i (i = 1,…, n).

-Key producers Sk ₁ , Sk ₂ ,.. , Share Sk _n to create a new shared secret SSk

-Insert the joint watermark W for joint proof of ownership into the entire work I _T using the shared secret key SSk

2.3 Multiple Watermark Extraction Method

The method of extracting the watermark W to prove the joint ownership of 3D data IT = (I1, I2, ..., In) is similar to the method of embedding except using the 3D secret watermark extraction algorithm.

-Generate a shared secret key SSk through Key Sharing Protocol (KSP) by receiving the author's O _i secret key Sk _i for all works I _i (i = 1,…, n)

-Watermark W extraction for joint ownership proof for entire asset I _T using shared secret key SSk and 3D secret watermark extraction algorithm

Also, in order for each author O _i have to claim ownership of their work I _i using his private key Sk _i and 3D Secret watermark extraction algorithm on the entire work I _T extract the watermark Wi.

3. Safety Analysis of MDWF

When implementing the MDWF described earlier, the algorithm uses a secure communication channel. Therefore, the security of MDWF depends on the security of the key sharing protocol and 3D secret watermarking algorithm used.

3.1 Security of Key Sharing Protocol

The key sharing algorithm proposed by the MDWF differs from the safety goals of the existing key sharing protocol in that each user cannot obtain any information about the shared key as well as other users' private keys [Menezes et. al., "Handbook of Applied Cryptography", CRC Press LLC, 1997]. In case of the key sharing protocol using TTP, the reliability of TTP is guaranteed and in the case of the key sharing protocol using MPT, the safety of multi-user operation can be secured [O. Goldreich, "Secure Multi-Party Computation", Manuscript, 2002, (Version 1.4)]. Therefore, MDWF's key sharing protocol can achieve perfection that no information about the private key of any user can be obtained from the information of the shared secret key.

The completeness of the key sharing protocol should not be able to obtain information about Sk _i from the information H (Sk _i ) for the shared secret key, which is based on the preimage resistance of the hash function.

3.2 Safety of 3D Secret Watermarking Algorithm

The 3D watermarking algorithm used in the MDWF proposed in the present invention is particularly robust to mesh simplification attacks. Zhang et al., "A Novel Watermarking Framework for Joint-Creatorship Protection", Proceedings of Cyberworlds 2005, Singapore, pp. 109-116, Nov. 2005] show robustness in mesh simplification of up to 36% of the original number of faces. 4 to 6 show an example of a mesh simplification attack. The left figure of FIG. 4 is an example model having a mesh representation of 10648 triangles, and the right figure is a model in which a watermark is inserted into the example model. To be inserted in blue). FIG. 5 is a model diagram after a mesh simplification attack and illustrates a case where a mesh representation of 5262 triangles is performed by performing a 50% mesh simplification, and FIG. 6 illustrates 9569 triangles by performing a 10% mesh simplification. A model with a constructed mesh representation. According to the experiment, the watermark inserted in FIG. 6 can be extracted, but the watermark inserted in FIG. 5 was not extracted.

The present invention allows the creators of 3D data to be collaborated to prove ownership of their contributions to the creation of the entire data, while at the same time demonstrating joint ownership of the entire asset, It aims to propose a framework to prevent unity. To this end, MDWF has established Goldreich [O. Goldreich, "Secure Multi-Party Computation", Manuscript, 2002, (Version 1.4)] utilizes the 3D secret watermarking technique, which uses the property of inserting multiple watermarks. In MDWF, in the sharing of producers 'private keys, the creators who participated in the sharing were able to propose a new type of key sharing protocol that prevents the producers from obtaining information about other producers' private keys as well as shared secret keys. Can be prevented. In addition, MDWF security is based on the security of key sharing protocols and 3D watermarking algorithms, which is ensured by the choice of secure hash functions and robust 3D watermarking.

Claims (3)

Total assets of the 3D data _T {I _{where, I T = (I 1,} I 2, ..., I n), n } is an integer of 2 or more co-producers involved in the production of O _1, O _2, ... , The secret key Sk _1, Sk _2, generated by the O ... _n , Inserting a secret watermark of each creator O _i into each asset I _i (i = 1, 2, ..., n), using Sk _n respectively, The secret keys Sk ₁ , Sk ₂ ,... Through the Key Sharing Protocol (KSP). , Sk _n , and the secret keys Sk ₁ , Sk ₂ ,. Generating a shared secret key SSk through an operation of Sk _n , and Embedding a joint watermark in the entire work I _T using the shared secret key SSk. The method of claim 1, wherein the shared secret key SSk is generated by a hash operation satisfying the following equation: Equation _{SSk = H (Sk 1 · Sk} 2 · ... · Sk n) In the above equation, H means a hash function. The method of claim 1, wherein the shared secret key SSk is generated by a hash operation satisfying the following equation: Equation SSk = H (Sk ₁ Sk ₂ ... Sk _n ) = H (Sk ₁ ) H (Sk ₂ ). H (Sk _n ) In the above equation, H is a hash function and satisfies H (a) H (b) = H (ab) for all inputs a and b.

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