International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved.
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A Review Of Watermarking With Their Attacks And Solutions In 3 D Geometry
Anuj Mangal1, Ambika Jain2 Deptt of computer Science
BSACET, Mathura
[email protected]1, [email protected]2
Mrs. Durga Puja
Department of Computer Science BSACET, Mathura [email protected]
Abstract—A watermark inserts an invisible signal inside the data (image, video and audio), for a number of reasons, which includes embedding copyright and caption information. In this paper, we first outline the introduction of 3D watermarking and then give the basic requirements of 3D watermarking.
Fundamental attacks and their solutions on 3D geometry watermarking is then reviewed. The past work was concerned with hiding the data, irrelevant of distorting the signal or tinkering the data with the intention of removing a watermark.
In contrast the watermarks are popularly used to avail strength in signal alteration, managing copyright issue, and preventing changes. Several recent approaches that quotes these issues are discussed in this paper.
Keywords— text, image, video and audio watermarking; polygonal meshes; spatial and transform domain based watermarking techniques.
I. INTRODUCTION
As a result of the vast growth in digital multimedia technologies, the intolerable copying of a digital content has resulted to a need of content ownership i.e. copyright protection. Watermarking is a solution to this problem [1]. A watermark, which is a secret indiscernible text, is imprinted into the original information in such a manner that the content quality remains acceptable. The proprietor of the original work can testify originality by excerpting the watermark from the data.
The demonstration of digital watermarking is given in Fig 1.
A message is imperceptibly embedded into the original visual content at the embedder. Then, the embedded content is delivered through a channel. This channel might represent degradations, transformations and possible signal processing operations on the visual data. Next, the watermark message is tried to be detected from the available content at the detector.
The detector may also utilize the original data during detection, depending on the application.
The need of 3D digital data has been popularly used in telecommunication, hardware designing, multimedia, motion etc. These 3D data are generally characterized by polygonal
meshes, which generates distortion during filtration, compression, watermarking operations. These alteration changes the visual quality of the 3D content.[2] Since many existing processing algorithms (e.g. simplification watermarking compression) are determined and/or evaluated by simple metrics like Hausdorff distance and Root Mean Square errors (RMS), which are not associated with the
human vision. The visual quality ranges from good (top row) to poor (bottom row). So this includes some quality. To produce distorted visual impact, of a distorted 3D model with respect to a reference (distortion-free) model is their main goal.
Fig 1 General scheme for watermarking
A 3D model containing some hidden data (stego-model) is the main intention of 3D watermarking. If an algorithm does not need the original content to recover the embedded data is called blind (on divergent, the algorithm is called non-blind);
an algorithm is detectable, if it can find watermark presence/absence , readable if it is able to read the watermark without prior knowledge.[3]
II. PREREQISITES OF 3DGEOMETRY WATERMARKING A watermarking system proposed for a 3D object should satisfy the necessities on capacity, imperceptible and robustness, these are the same attributes that required for video and image watermarking.
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved.
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The system should be able to insert important data, satisfying capacity property. Also, watermarking algorithm should discriminate between numerous watermarks with a less error ratio with the increased watermarked edition of a digital data [5]. This requirement is useful in public watermarking designing, where different watermarks are applied over each content for different buyer. The capacity requirement of image and video watermarking has no major differences.A second requirement is imperceptible, that minimizes the change effect in the geometry because of watermarking.
However, the imperceptibility prerequisite for a these models are more complicated and of major concern, as compared to that of video and image watermarking.
In addition to these requirements, to prevent the visual aspect of the geometric model from getting despoiled, a watermarking system should be robust to all topological or geometric operations. These operations on the model may include the following [6]:
• Rotation, uniform scaling and translation.
• Points randomization.
•Polygon simplification (required to achieve sufficient rendering speed)
• Smoothing mesh operations.
• Re-meshing (re-triangulation); producing equal sized and shaped patches
• Slice(cutting and sectioning) operations—slicing parts of the model.
• Deformations applied on local level.
The below section depicts the problems related to 3D geometry model watermarking and their proposed solution.
III. FUNDAMENTAL ATTACKS AND THEIR SOLUTIONS IN 3DGEOMETRY WATERMARKING
The 3D geometry model watermarking has some specific attacks and their solutions which are tabulated in Table 1 [10]
Table 1 Attacks and solutions in 3D watermarking Attacks Anticipated Solutions
1.Translation • Placing an object in such a way that mass center corresponds with the original coordinate system [7]
• earlier for embedding, invariant metrics are used for translation (e.g. a pair of angles in a triangle of a mesh [8], [9] ) 2.Rotation • Rotating an object in such a way that its
principal component get matched with the coordinates of z-axis [7].
• earlier for embedding, invariant metrics are used for rotation (e.g. a pair of angles in a triangle of a mesh [8], [9] ) 3.Scaling • Standardizing the vertices of radial
components in such a way that the distance of the farthest vertices to the source is always equal to one [11].
• earlier for embedding, invariant metrics are used for scaling (e.g. a pair of angles in a triangle of a mesh [8], [9] )
4.Affine Transformation
•The distortions caused by affine transformation are recovered and estimated by original mesh [12].
•Inserting watermark into invariant metrics under affine transformation (e.g.
ratio of the volumes of a pair of tetrahedrons in a mesh model [8], [9]) 5.Cropping •Scrambling allows distribution of
information regarding watermark over entire model [12].
•Distributing the watermarks on various exterior patches of mesh model and using the normal vector distribution of each patch for watermark embedding [13].
6.Additive Noise • After frequency based transformation watermark is embedded into the coefficients of every resolution, which is applied to the mesh model. (Transform Domain Methods,[14], [15])
7.Compression •After frequency based transformation, watermark is inserted into the coefficients of every resolution, which is applied over mesh model. (Transform Domain Methods,[14], [15])
8.Mesh Simplification
•Watermark is inserted to each set of vertices, rather than one vertex [7].
• By using the original mesh connectivity, the attacked mesh can be re-sampled [16].
• earlier for embedding, invariant metrics are used for mesh simplification such as normals of collections of surfaces [17].
9. Remeshing • Using invariant metrics under mesh simplification, such as normals of collections of surfaces, as an embedding
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved.
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primitive [17].• By using the original mesh connectivity, the attacked mesh can be re-sampled [16].
IV. ATOUR OF 3DWATERMARKING ALGORITHMS In this section, we present a review of proposed watermarking algorithms. This is unlikely to be a complete list and omissions should not be interpreted as being inferior to those described here.
Watermarking for NURBS representations is comparatively new concept to engineering CAD regardless of the popularity of NURBS surface and curves. Ohbuchi et al. [18] proposed a new data embedding algorithm which by using rational linear function, NURBS curves and surfaces can be reparameterized, whose coefficients are modified for encoding data purpose. The exact geometric shape is conserved. However the watermark related information, can be easily ruined by reparameterization or reapproximation of the exterior(surface).
Watermarking on Constructive Solid Geometry (CSG) models was completed by Fornaro and Sanna [19]. By using a hash function, watermark can be easily extracted; and for encryption and decryption of the watermark, public key algorithm is used. Watermarks were stored at two place: solid and comment nodes. For storing watermark in solid, a newly created watermark node is linked to the CSG tree(original).
For comment nodes, the watermark information can be inserted without changing the model.
There are few fragile algorithms authenticating the reliability of 3D models. Yeo and Yung[32] introduced the first fragile watermarking of 3D objects for verification purpose. As these algorithm could easily crack the authentication mechanism because their algorithm relies heavily on the transformation operation and vertex position, which does not affect the integrity of mesh model.
Ohbuchi et al. (1997) [33]: The Triangle Strip Peeling Symbol sequence (TSPS) embedding algorithm is related to topological embedding based on public watermarking scheme. This algorithm stuffs bits while rendering over mesh.
However, TSPS implementation has two prominent problems:
It needs bit human intervention. Since it is based on the topology modification and an opponent can easily locates the payload, so we can say it is unsecure.
Ohbuchi et al. (1997): ‘Polygon Stencil Pattern (PSP)’ this algorithm produces watermarks called as Polygon Stencil Pattern (PSP) embedding, which are quite strong against various polygonal simplification algorithms. The reason behind this is as many polygon simplification algorithms preserves the boundary value of polygonal strips and stencil meshes. If intentionally, vertices on the boundary are changed or distorted (as some polygon simplification algorithms do), flaw will appear, which will ultimately degrade the quality of model.
Mao et al. (2001) [20] Here the robust watermarking on object space is addressed. As with the help of existing triangulation software, polygonal mesh can be transformed into a triangle mesh. In which the ration of two line segments over same line do not change under affine transformation.
This algorithm has the advantage of high space efficiency as compared with geometrical primitives based algorithms.
Bors (2004a, 2004b, 2006)[21][22][23] developed new digital watermarking methodology for 3D graphical objects shapes. The proposed watermarking algorithms embeds watermark over vertices fulfilling certain geometric norms.
Two different techniques were considered for information embedding. These techniques were based on parallel planes and bounding ellipsoids which differentiates how the local neighborhood is represented geometrically. These watermarks were tested for noise disturbances in 3D shape structure as well as to 3D object cropping. Apart from having robustness against rotation, uniform scaling, translation and also cropping, it had odd against mesh simplification attacks.
Zafeiriou,[7] applies watermarking of 3D models, which are focused on using mesh information(vertices) and random connectivity(edges). This is helpful for copyright protection and handling of mesh simplification attacks. This is the first blind 3D watermarking method dealing with geometric attacks and mesh simplification.
Barni et al. (2004):[24] This algorithm, as per spherical pseudo-random bumped surface, changes the vertices cordinates of 3D model.
The watermark is encoded by the amplitude and pseudo- random position of the bumps. Watermark is recovered by a typical correlation detector. This algorithm is suitable for watermarking 3D objects with a reasonably large number of faces.
Benedens[25] described a method dealing with detection of watermarking process and mesh affine registration. This is used in order to compensate for affine transformations. Main disadvantage of this algorithm is that it is not blind because of the registration method requiring both the test 3D and original model.
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved.
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Song et al.[31] proposed further watermarking algorithm which is strong against rotation, translation, Gaussian attack, scaling and mesh simplification. This algorithm makes an image from mesh and then inserts the watermark by using specific image-based watermarking techniques. This algorithm falls in non-blind category as it requires additional information for detection of watermark.Earlier, Ohbuchi et al. [26] proposed a numerous techniques for inserting data in 3D polygonal objects. Further, there are two attributes that can be used for inserting watermark in 3D models: the topology (connectivity) information and the geometry (coordinate) information. The TSQ extraction algorithm does not need the guarantee of extracting the original cover-3D-object. However, there is need to obtain a pair of values identifying marker triangles. Watermarks obtained by TSQ algorithm cope up with rotation, translation, and uniform scaling changes. However, they can be destroyed by other disturbances, like randomization of coordinates, by geometrical transformation (general class), or by a wide range of topological variation (re-meshing).
Further, Ohbuchi et al. [28] proposed more robust watermarking algorithm inserting watermark into mesh spectral domain, improvising computational efficiency and attack resistant for 3D polygonal meshes.
Wu and Cheung [29] introduced a fragile watermarking scheme for verifying 3D mesh models. Watermarks obtained by this algorithm cope up with translation, rotation, and uniformly scaling, but perceptive to other actions. It has few pitfalls. Firstly, the center location of mesh will always get changed if there is change in any vertex, so it will get failed in locating the changed regions. Secondly, since it is a semi- public watermarking model i.e. it requires original watermark in detecting stage to verify watermarked model. Pure public watermarking scheme is more preferred in fragile watermarking in order to avoid extra cost for encrypting the original watermark.
Chou and Tseng [30] proposed a multi-function vertex embedding method and an adjusting-vertex method to mitigate the tampering and convergence problems.
V. CONCLUSION
In this paper we have mentioned various type of watermark, which are widely used to encode copyright information.
Robustness to signal distortions and resistant to alteration are some of its important necessity. In order to achieve this, embedding position of watermark in the regions of the audio, video or image data is of important consideration. However, the signal to noise ratio (SNR) must be kept small in order to make watermark noticeable.
We then outlined some fundamentals attacks on the 3D models and their solutions.
Finally, we surveyed many methods for watermarking and identified their potencies and weak points.
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