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Robust Mesh-based Hashing for Copy Detection and Tracing of Images
Chun-Shien Lu, Chao-Yong Hsu, Shih-Wei Sun, and Pao-Chi Chang
Proc. IEEE Int. Conf. on Multimedia and Expo: special session on Media Identification, Taipei, Taiwan, 2004
Reporter: Jen-Bang Feng
2
Outline
Watermarking and Hashing The Proposed Method Conclusions
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Watermarking and Hashing Digital Watermarking (Data Hiding)
Content has to be modified (a data hiding technique) Contents to be protected must be watermarked Measures “originality” Stand-along
Media Hashing (Fingerprinting) Content is not modified (a non-hiding technique) Can track the usage of contents already available in
the public domain Measure “similarity” Connection to database required
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Robust Signal Hashing Problem
Hash(Baboon)= XXX…
Hash(Lena)= YYY…
Hash(Lena 2)= ZZZ…
Should be very different
Should be sufficiently similar
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Perceptual Hashing The fragility of cryptography
hashing is too restricted Media data permits acceptable
distortions Media hashing needs
Robustness (error-resilience) Collision-free Fast searching (complexity) Scalability
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Track 1Track 1
Architecture for Robust Identification of Media Content
Track
Track 1Track 1Meta data
FingerprintGenerator
Database
CompareFingerprintGenerator
Test Track
If matchReturn Track ID Confidence
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The Proposed Method
DWTOriginalimage
Harrisdetector
Delaunaytesslation
Meshnormalization
Mesh-basedHash extraction
Lowest-frequencycomponent
Mesh generation
Normalizedmeshes
Hash sequence
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The Proposed Method
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Mesh Normalization
A
B
C
Mk
A’ B’
C’
Mknorm
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Mesh-Based Hashing
32
32
4x4 DCTTotal 64 blocks
otherwise.,0
ones,larger theis 1 if,1 sk
k
ACsH
64 bits per mesh, half 1’s and half 0’s
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Conclusions
The number of 0’s and 1’s are the same
Collision-free Robust against attacks
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Watermark AttacksWatermarking Attacks
RemovalAttack
GeometricalAttack
CryptographicAttack
ProtocolAttack
DenoisingLossy compressionQuantizationRemodulation Collusion Averaging
Global, local warpingGlobal, local transformsJittering
Brute force key searchOracle
Watermark inversionCopy attack
Voloshynovskiy et al. “attacks modeling: towards a second generation watermarking benchmark,” Signal Processing, 2001Kutter and Petitcolas, “A fair benchmark for image watermarking systems,” Proc. SPIE99
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Harris Detector
where I(x, y) is the grey level intensity and where A represents the integration of A on a given neighborhood. If at a certain point the two eigenvalues of the matrix are large, then a small motion in any direction will cause an important change of grey level. This indicates that the point is a corner.
2
2
,
yI
yI
xI
yI
xI
xI
M
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Harris Detector The corner response function is given
by:
where k is a parameter set to 0.04 (a suggestion of Harris). Corners are defined as local maxima of the cornerness function. Sub-pixel precision is achieved through a quadratic approximation of the neighborhood of the local maxima.
2det MtrkMR
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Delaunay Triangulation Voronoi Diagrams
每一點皆屬於最靠近的一區 http://infoshako.sk.tsukuba.ac.jp/~to
hyama/voro/edelacli.html