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Pattern-based Data Hiding for Binary Image Authentication by Connectivity-preservingHuijuan Yang, Alex C. Kot, IEEE Fellow
IEEE Transactions on Multimedia, Vol. 9, No. 3, Apr. 2007Multimedia Security Final Project
R97922062 葉容瑜 R97922003 程瀚平
Introduction Proposed Method The Authentication Mechanism Experimental Results Conclusions
Introduction(1/3) Digital documents
Ex. certificates, digital books, fax, personal documents How to ensure the authenticity and integrity of
digital documents, as well as detection of tampering and forgery, become a serious concern
Powerful image editing software Data hiding for binary images authentication has
been a promising approach to alleviate these concerns
Introduction(2/3) Data hiding on binary images can be done
the lower level: flipping pixels from black to white and vice versa
the higher level: modifying width of strokes and spacings between characters and words
In this paper, our focus is on data hiding for binary images in lower level for the purpose of image authentication
Introduction(3/3) Define a “connectivity-preserving” criterion to
assess the “flippability” of a pixel Connectivity among pixels plays an important
role to their visual qualities
Wu et al.’s approach Proposed approach
Visual distortion ConnectivitySmoothness
4-connectivity8-connectivity
Uneven embeddability of the image Shuffling
Embeddable blocks/Embeddable pixels(cryptographic signature)
The Main Objectives1. Assess the “flippability” of a pixel using the connectivity-
preserving criterion to achieve good visual quality of the watermarked image
2. Handle the “uneven embeddability” of the image by adaptively embedding the watermark only in those “embeddable” blocks
3. Study the invariant features in flipping pixels in binary images to achieve blind watermark extraction
4. Explore different ways of partitioning the image to achieve larger capacity
5. Investigate on how to locate the “embeddable” pixels in the watermarked image so as to incorporate cryptographic signature to achieve higher security
Introduction Proposed Method
Flippability DecisionBlock PartitionEmbeddabilityCapacitiesWatermark Embedding and Extraction
The Authentication Mechanism Experimental Results Conclusions
Flippability Decision Flippability
The transitions from the pixel to its eight neighbors in a 3 * 3 block
In particular, the 4- and 8-connectivity among pixels
VH TransitionIR TransitionC Transition
VH Transition Nvw: the number of uniform white transitions
along vertical and horizontal directions Nvb: the number of uniform black transitions
along vertical and horizontal directions
Black: 1White: 0
Nvw = 0, Nvb = 2 => Nvw = 0, Nvb = 0
Nvw = 0, Nvb = 0
=> Nvw = 0, Nvb = 0
IR Transition Nir: the number of the interior right angle
transitions
Black: 1White: 0
Nir = 0
=> Nir = 1 Nir = 0
=> Nir = 0
C Transition Nc: the number of transitions from the center
pixel to the sharp corners
Black: 1White: 0
Nc = 1
=> Nc = 0
Nc = 0
=> Nc = 0
Flippability/Connectivity-Preserving Criterion Flippable
VH transition, IR transition, and C transitionremain the same before and after flipping the center pixel
Flip the pixel will not Destroy the connectivity b/w pixels in the
neighborhood(VH)Create extra clusters as well(IR)Destroy the 8-connectivity among pixels(C)
By satisfying the “Connectivity-Preserving” criterion, the local connectivity is preserved
Block Partition Several different types of blocks
Fixed 3*3 block (FB)Non-interlaced block (NIB)Interlaced block (IB)
Embeddability Determined pixels
Non-interlaced block scheme:all pixels except the boundary pixels
Interlaced block scheme:all pixels except those lie in the sharing rows and columns
The embeddability of a block depends on the “flippability” of the determined pixels in the block
Capacities Only one pixel is flipped in each block=> The prob. of a pixel to be “flippable” in a block is
independent to other pixels Assume the probability that a pixel satisfies the
“Flippability Criterion” is pFB: The prob. of each block to be “embeddable” is pNIB: The prob. is 1 – (1-p)^(n-2)2
IB: The prob. is 1 – (1-p)^(n-2)2
A larger block size definitely will increase the prob.for a block to be “embeddable”, however, the total number of blocks will be decreased
=> Decrease the capacities
Watermark Embedding1. Partition the image into equal size square blocks, note that
the block size does not need to be square2. Determine the flippability of the determined pixels based on
the “Flippability Criterion”3. Once a pixel is identified as “flippable”, the block is marked
as “embeddable”. The current “flippable” pixel is identified as the “embeddable” pixel, i.e., “embeddable” location of the block
4. Proceed to the next block5. Repeat steps 2 to 4 until all the blocks are processed6. Embed the watermark in the “embeddable” blocks by flipping
the “embeddable” pixels (if needed) to enforce the odd-even feature of the number of black or white pixels in the block
Embeddable pixels = flippable pixels Flipping a pixel in a block may affect
the “flippability” of the pixels in the same block but not the pixels in its neighboring blocks
The “embeddability” of a block is invariant in the watermark embedding processThe “flippability” of a pixel is invariant in the watermark
embedding processA “flippable” pixel which is identified as “embeddable”
is still “flippable,” hence an “embeddable” block remains “embeddable”
The watermark can be extracted blindly from the “embeddable” blocks by computing the odd-even feature of the number of black or white pixels
Introduction Proposed Method The Authentication Mechanism
Locate “Embeddable” Pixels CriterionAuthentication ProcessThe Verification Process
Experimental Results Conclusions
Locate “Embeddable” Pixels Criterion The odd-even enforcement is employed for the
watermark embeddingVulnerable to the “parity attack”Ex: an adversary can carefully flip two pixels in the same block while keeping the odd-even feature of the block unchanged.
Locate “Embeddable” Pixels Criterion p-4 condition
Flipping the pixel that does not change the “flippability” of its previous four (p-4) neighbors that lie in the same 3 x 3 block
d-2 conditionFlipping the pixel that does not affect the
“embeddability” of those d-2 pixels (determined pixel) that have already been processed in the same block
Locate “Embeddable” Pixels Criterion
Authentication Process
The Verification Process
Introduction Proposed Method The Authentication Mechanism Experimental Results
Capacity and VisibilityTest Locating Embeddable Pixels Criterion and
Authentication MechanismComparisons
Conclusions
Capacity and Visibility
Capacity and Visibility
Capacity and Visibility
(a)The original text image of size 336 x 336 (Chinese)
(d) Hide 482 bits by FB 3 x 3
(e) Hide 733 bits by NIB 4 x 4
(f) Hide 1261 bits by IB 4 x 4
Capacity and Visibility
(b) The original text image of size 336 x 336 (English)
(g) Hide 447 bits by FB 3 x 3
(h) Hide 672 bits by NIB 4 x 4
(i) Hide 1237 bits by IB 4 x 4
Capacity and Visibility
(b) The original text image of size 336 x 336 (Handwritten)
(g) Hide 313 bits by FB 3 x 3
(h) Hide 554 bits by NIB 4 x 4
(i) Hide 972 bits by IB 4 x 4
Capacity and Visibility Evaluate the visual distortion caused by flipping
pixelsThe visual distortion table proposed by Wu et al. is
employed.
M. Wu and B. Liu, “Data hiding In binary images for authentication and annotation,” IEEE Trans. Multimedia, vol. 6, no. 4, pp. 528–538, Aug. 2004.
)(1)( iFCiDS
Capacity and Visibility Distortion score (DS)
Total distortion (TD)
Average per pixel distortion (APPD)
)(1)( iFCiDS )(1)( iFCiDS
n
i
iDSTD1
)(
nTDAPPD /
Capacity and Visibility
)(1)( iFCiDS
Test Locating Embeddable Pixels Criterion and Authentication Mechanism
(a) The original image of size 920 x 230
(b) Hide 1056 bits by proposed algorithm with FB 3 x 3
(c) The watermarked image that is tampered
(d) The original logo image
(e) The reconstructed logo image when no tampering occurs
(f) The reconstructed logo image when the watermarked image has been tampered
Comparisons
(a) Original image of size 173 x 115
(b) The proposed method (c) Wu et al. method
(d) Tseng et al.
(e) Lu et al.
(f) Yang & Kot
111 bits180 bits260 bits
Introduction Proposed Method The Authentication Mechanism Experimental Results Conclusions
Conclusions A novel blind data hiding scheme for binary
images authentication based on connectivity-preservingA window of 3 x 3 is employed to access the
“flippablility” of a pixel in a block
Different types and sizes of block can be chosen cater for different applications
The proposed scheme can be applied to a wide variety of binary image authentication