Multimedia Content Protection through Reversible ......Multimedia Content Protection through...
Transcript of Multimedia Content Protection through Reversible ......Multimedia Content Protection through...
Multimedia Content Protection
through Reversible Watermarking:
Theory and Implementation
Ruchira NaskarRajat Subhra Chakraborty
Department of Computer Science and Engineering
Indian Institute of Technology, Kharagpur
Email:{rschakraborty,ruchira}@cse.iitkgp.ernet.in
8th International Conference on Information Systems Security
December 15-19, 2012
Ruchira NaskarPh.D. Student
Rajat Subhra ChakrabortyAssistant Professor
Contents� Digital Watermarking
� Reversible Watermarking� Overview
� Applications
� Motivation behind Research� Motivation behind Research� A Case Study
� State-of-the-Art� Five Broad Classes of Reversible Watermarking Algorithms
� Challenges Involved� Embedding Retrieval Information
� Minimizing FRR of Cover Image Pixels
� Probable Solutions2
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Contents� Implementation Issues
� Efficient Implementation: Parallel Processing
� Efficient Implementation: on FPGA
� Evaluation of Reversible Watermarking Algorithms� Software Evaluation� Software Evaluation
� Theoretic Evaluation
� Conclusion
� Bibliography
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Digital Watermarking
Cover Data
Watermarked
Content to be protected
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Embedder
Watermark
WatermarkedData Extractor
Extracted Watermark
Information about Cover Data
Digital WatermarkingPerceptible Watermarking
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Imperceptible Watermarking
Reversible WatermarkingBit-by-bit reversal
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Reversible Watermarking:
Applications
� 100% Cover Data Recovery
� Needed in highly security sensitive industries such as:
� Military
� Medical
Legal
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� Legal
� Authentication of Digital Data
� Overwhelming majority of algorithms proposed are for grayscale images
Motivation behind Research in
Reversible WatermarkingReversible Watermarking
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• Digital watermarking in the medical industry provides content
protection and integrity preservation of medical data, e.g. patient
images electronically transmitted over insecure channels in
telemedicine
• Electronic Patient Records (EPRs) kept embedded in form of
A Case Study from the Medical
Industry
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• Electronic Patient Records (EPRs) kept embedded in form of
watermark, into medical images
- Useful for doctors, patients, clinical researchers,
insurance companies, hospitals
• Often responsible for information-loss:
- Cover data distortion caused due to watermark embedding
- Cannot be removed by general watermarking
- Highly undesirable in the medical industry
Aims:
• To investigate the effects of DRM, specifically digital
watermarking, on medical imaging applications
•
A Case Study from the Medical
Industry
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• To investigate the need of 100% reversibility provided by
reversible watermarking
Automated Diagnosis of Malaria
• Malaria infection caused by Plasmodium vivax is a leading
cause of death world-wide
• Existing manual methods of malaria diagnosis, are tedious
and error-prone
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• Hence the need for computer-aided automatic diagnostic
systems
Methodology
• Blood smears of 250
patients collected from
Midnapore Medical
College and Hospital and
Medipath Laboratory, W.B.Lossy
Technique
Reversible
Technique
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Medipath Laboratory, W.B.
• According to doctors’
suggestions 50 best
prepared blood smears
were selected as our test
images
e e
e
Malarial Prediction Model*
• Total 26 features were extracted to distinguish the healthy and
malaria infected erythrocytes
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malaria infected erythrocytes
• Those features include
- Geometric features, e.g. area, parameter, circularity
- Haralick Textural features, e.g. entropy, correlation, dissimilarity
• The Multivariate Logistic Regression Model was used for prediction1
* D. Das, M. Ghosh, C. Chakraborty, A.K. Maiti, M. Pal, “Probabilistic Prediction of Malaria using Morphological and Textural Information”, Proceedings of International Conference on
Image Information Processing (ICIIP) 2011, Nov. 2011.
Results
Original Test Images
Test Images containingResidual Distortions
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AlgorithmResidual Distortion
(PSNR)Embedded bpp
LSB-substitution
Entire Image
G Component
Entire Image
GComponent
51.1421 55.9077 3.00 1.00
Distortions
Residual Image Distortion (after Watermark Extraction) and Embedded Watermark Size *
*Results averaged over 50 test images
ResultsClass Conditional Density Plots
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(a) Original Test Images (b) Distorted Test Images
(a) Original Test Images (b) Distorted Test Images
ResultsClass Conditional Density Plots
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(a) Original Test Images (b) Distorted Test Images
(a) Original Test Images (b) Distorted Test Images
Results
• Overall Prediction Accuracy was measured as:
where Phealthy = number of predicted healthy erythrocytes
Prediction Accuracy
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where Phealthy = number of predicted healthy erythrocytes
Nhealthy = number of erythrocytes actually healthy
Pinfected = number of predicted infected erythrocytes
Ninfected = number of erythrocytes actually infected
ResultsPrediction Statistics for Original Test Images
ActualPrediction Accuracy (%)
Infected Healthy
PredictedInfected 79 11 87.78
Healthy 8 178 95.70
Overall Prediction Accuracy (%) 91.74
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Prediction Statistics for Test Images containing Residual Distortion after Lossy Watermarking Extraction
Actual Prediction Accuracy (%)Infected Healthy
PredictedInfected 74 16 82.22
Healthy 12 174 93.54
Overall Prediction Accuracy (%) 87.88
Inferences
• The accuracy of prediction drops considerably due to residual
distortion caused by lossy watermarking
• Reversible watermarking can restore the watermarked images to
their original forms without any distortion
• The accuracy of prediction performed on the restored images, is
as high as what is achieved from the original images
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Prediction Statistics for Test Images Restored by Reversible Watermarking
Actual Prediction Accuracy (%)Infected Healthy
PredictedInfected 79 11 87.78
Healthy 8 178 95.70
Overall Prediction Accuracy (%) 91.74
Typical Classes of Reversible
Watermarking AlgorithmsWatermarking Algorithms
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1. Integer Transform
Cover Image
Average (l), Difference (h)
Embed{0,1}b∈Watermark bit b 2h h' +=
Transform adjacent pixels (x, y)
yx h ;2yx l −=+=
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Watermarked pixels (x’, y’)
Inverse Transform (l, h’)
−=++=2h' l y';
21h' l x'
Watermarked Image
J. Tian, “Reversible data embedding using a difference expansion”, IEEE Transactions on Circuits
Systems and Video Technology, 2003
2. Data CompressionL-level quantize each pixel x:
QL(x) = L ;
RL(x) = x - QL(x)Cover Image
WatermarkW
Quantized ValuesQL(x)
RemaindersRL(x)
LosslessCompression
Concatenate
L
x
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W
Bit Stream H
Convert to L-ary Symbols
L-ary Symbols{0, 1, …, L-1}
+
∈Watermarked
Image
M.U. Celik, G. Sharma, A.M. Tekalp and E. Saber, “Lossless generalized-LSB data embedding”,
IEEE Transactions on Image Processing, 2005
3. Histogram Bin Shifting
…
0 1 … 254
Peak
…
Right-Shifted
0 1 … 255
Frequency
Frequency
CoverImage
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…
0 1 … 255
‘0’‘1’
WatermarkedImage
Frequency
Z. Ni, Y.Q. Shi, N. Ansari and W. Su, “Reversible data hiding”, IEEE Transactions on Circuits and
Systems for Video Technology, 2006
4. Pixel PredictionPredict pixel x
x‘ =Predict (x, Neighboring pixels of x)
Cover Image
Predicted Pixel x ’
Compute Prediction Error
e = x – x‘
Original Pixel x
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+
WatermarkedImage
e = x – x‘
Embed
{0,1}b∈Watermark bit
b)|e|(2sign(e)e' +××=
L. Luo, Z. Chen, M. Chen, X. Zeng and Z. Xiong, “Reversible image watermarking using
interpolation technique”, IEEE Transactions on Information Forensics and Security, 20108th International Conference on Information Systems Security
Cover Image
IDCT
xx x
x xx xx
x xxxxxxxxxxxxxxxx
Left Shift&
Embed bits
InverseIDCT
8
8
8
8
Divide into 8X8 blocks
5. Invertible Integer DCT
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B. Yang, M. Schmucker, W. Funk, C. Busch and S. Sun, “Integer DCT based reversible
watermarking technique for images using companding technique”, Proceedings of SPIE, 2004.
Watermarked 8X8 block
xxxxxxxxxxxx
x x xx
Select IDCTcoefficients
Embed bits
Watermark
IDCT
WatermarkedImage
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Challenges InvolvedChallenges Involved
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Challenge 1: Embedding
Retrieval Information� Primary requirement of reversible watermarking: To restore the
cover data back to its original form bit-by-bit
� Additional retrieval information needed for bit-by-bit cover data
retrieval
� Retrieval information and the watermark together form the payload
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� Retrieval information and the watermark together form the payload
to be embedded
� Example of retrieval information:
� Location Map: A bit string to distinguish between cover data positions with
and without having watermark bits embedded
� Used widely in several state-of-the-art reversible watermarking algorithms
� Challenge: To reduce the size of this retrieval information
overhead, therefore to improve pure watermark embedding capacity
Use of Location Map: An Example
Predict pixel xx ’ = Predict (x, Neighboring pixels of x)
Cover Image
Predicted Pixel x ’
Compute Prediction Errore = x – x ’
Original Pixel x
A Prediction based Reversible Watermark Embedding Algorithm
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+
WatermarkedImage
e = x – x ’
Embed
{0,1}b∈
b)|e|(2|'e| +×=
YesNo
|e|<threshold ?
Watermark bit
Use of Location Map: An ExampleA Prediction based Reversible Watermark Extraction Algorithm
Predict pixel xx ’ = Predict (x, Neighboring pixels of x)
Predicted Pixel x ’
WatermarkedImage
Compute Prediction Errore = x – x ’
Watermarked Pixel x
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+
e = x – x ’
Extract
b)/2|e(||'e||,2)emod(| b
−==
YesNo
threshold2-1|e| >
Restored Image
Use of Location Map: An ExampleOverhead Bits
• Error Threshold (k):
o Only those prediction errors with absolute values <k are used for watermark embedding
o Controls embedding capacity
• Location Map:
o Used to identify pixels capable of causing under/overflow, i.e.(p < 0) or (p > 255), where p is a watermarked pixel
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(pwm< 0) or (pwm> 255), where pwm is a watermarked pixel
o During extraction each watermarked pixel is tested for under/overflow.
o A pixel found capable of causing under/overflow during extraction, indicates one of the two possibilities:
o It was found to be capable of causing under/overflow during embedding, and hence was not used for embedding.
o Previously, it did not cause an under/overflow, but after embedding it has lost its embedding capability.
Use of Location Map: An ExampleWeighted Median based Prediction (R. Naskar and R.S. Chakraborty, IET Image Processing, 2012)
I. Select Base Pixels
II. Predict three sets of pixels consecutively, assigning appropriate
weights to the neighbors
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3Base Pixel
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0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
Base Pixel
First Set Pixel
Third Set Pixel
Second Set Pixel
Use of Location Map: An Example
Weighted Median based Prediction
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
W=1
Prediction Formula for First Set of Pixels:
ξ(p(i,j)) = WM({p(i -1, j-1), p(i -1, j+1), p(i+1, j -1), p(i+1, j+1)}, {1, 1, 1, 1})
W=1
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2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
Pixel to be predicted
Neighbor with assigned
weight ww
Prediction of a First Set Pixel
W=1W=1
Use of Location Map: An Example
Weighted Median based Prediction
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
Prediction Formula for Second Set of Pixels:
ξ(p(i,j)) = WM({p(i, j-1), p(i -1, j), p(i, j +1), p(i+1, j)}, {1, 2, 1, 2})
Prediction Formula for Third Set of Pixels:
ξ(p(i,j)) = WM({p(i, j-1), p(i -1, j), p(i, j +1), p(i+1, j)}, {2, 1, 2, 1}) W=2
W=1 W=1
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0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
0 3 0 3 0 3 0 3 0 3
2 1 2 1 2 1 2 1 2 1
Prediction of a Second Set Pixel
W=2
W=1
W=1
W=2 W=2
Use of Location Map: An ExampleResults for Weighted Median based Prediction:
Embedding Capacity, Distortion, Location Map for Error Threshold
0 ≤ k ≤ 10 (Non-Zero Location Map for Higher k values)
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Use of Location Map: An Example
Results for Weighted Median based Prediction:
Embedding Capacity, Distortion, Location Map for Error Threshold
0 ≤ k ≤ 10 (Zero Location Map for all 0 ≤ k ≤ 10 )
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Challenge 2: Minimizing FRR of
Cover Image Pixels� In traditional reversible watermarking algorithms for digital images,
the watermark is a secure hash of the cover image (Eg. MD5, SHA)
� To authenticate the cover image at the receiver end:
� The extracted watermark is matched with the hash of the cover image
� If there is a match, cover image is accepted
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� If there is a match, cover image is accepted
� A hash mismatch indicates tampering of the cover image while
transmission
� If there is a hash mismatch the entire cover image is rejected
� This may occur even due to a single bit mismatch
� Number of cover image pixels falsely rejected is extremely high in such cases
� Challenge: To minimize the False Rejection Rate (FRR) of the
cover image pixels in case of authentication failure
Challenge 2: Minimizing FRR of
Cover Image Pixels
ReversiblyWatermarked
Image Extractor
Restored Cover Image Compute Hash
1 0 1 1 0 … 1
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Image Extractor
Extracted Watermark
Hash
Match
Yes No
Accept Cover Image
Reject Entire Cover Image
Cover Image Tampering and
False Rejection� Reversibly watermarked image rejection may be brought about by
� Intentional Tampering: Trivial for a man-in-the-middle adversary, reversible
watermarking being a fragile watermarking technique
� Unintentional Modification: For example, transmission through noisy
communication channel may modify one or more pixels of the cover image
� Unintentional Modifications are often found in military communications, and
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� Unintentional Modifications are often found in military communications, and
are bound to occur each time the image is transmitted
� The convention is to reject the entire watermarked image at the
receiver end if it fails authentication, since there is no way to detect
the exact location(s) of tampering
� Repeated rejection requires re-transmissions of the entire
watermarked image
� This feature may be exploited by an adversary to bring about a form
of “DoS” attack
Probable Solutions� Tamper Localization Mechanism: Localizing the area(s) of
tampering and selective rejection of tampered cover image area(s) in
case of authentication failure
� Reject only the tampered area(s) instead of the entire image
� Re-transmission of only the tampered region(s) of the image,
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� Re-transmission of only the tampered region(s) of the image,
instead of the entire watermarked image
� Also minimizes bandwidth requirement of the communication
channel
Probable Solutions� Determining the Region(s) of Interest within an image
� In various application domains of reversible watermarking, only some areas of
the image carry the bulk of the important information and are of interest to
the recipient
� If the tampering falls outside the region(s) of interest, the cover image is
accepted by the receiver, thus avoiding unnecessary rejection
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accepted by the receiver, thus avoiding unnecessary rejection
� Otherwise the user can request re-transmission of only the tampered parts of
the image
Implementation IssuesImplementation Issues
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Implementation Issues� Existing reversible watermarking algorithms involve various
complex mathematical operations for achieving reversibility property
� Invertible functions such as invertible integer transform, invertible IDCT
etc.
� Computation of Overhead Data such as cover image retrieval information
(location map), peak of pixel frequency histogram, thresholds etc.
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(location map), peak of pixel frequency histogram, thresholds etc.
� Lossless Compression Techniques such as JBIG, Run Length Encoding,
LZW encoding etc.
� Such operations are absent in the implementation of their non-reversible
counterparts
� Reversible watermarking algorithms suffer from large runtime
requirements due to these complex mathematical operations
Efficient Implementation:
Parallel Processing� However, many algorithms are block-based, and their processing can
be done in parallel
� Multi-threaded programming enables efficient software
implementations of reversible watermarking algorithms to exploiting
this parallelizability
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this parallelizability
� Multi-threaded implementation may be achieved by:
� Suitable computer architectures such as multi-core processors, GPU,
computer clusters
� Parallel processing provided by software such as MATLAB Parallel
Computing Toolbox, OpenCV Parallel Computing Descriptors, JAVA
Concurrency/Multithreading
Efficient Implementation:
Parallel ProcessingIDCT based Reversible Watermarking:
Divide into 8X8 blocks
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Parallel Processing
L L
Efficient Implementation: On
FPGA� Hardware Implementation of the Watermarking Algorithms can be
extremely effective in improving the processing time
� Field Programmable Gate Array (FPGA) based implementations are
attractive because of:
� Lower cost
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� Re-configurability
� Easy-to-use software provided by vendors
� Easy capabilities of interfacing with a PC
� Greater hardware and memory resources and dedicated arithmetic building
blocks for modern FPGAs
� Hardware implementations capable of meeting real-time constraints,
(if any)
Evaluation of Reversible
Watermarking Algorithms
� Parameters for evaluating watermarking algorithms performance:
� Embedding Capacity
� Cover Data Distortion
� Runtime Requirement
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� Two-way evaluation
� Software Simulations
� Theoretical Analysis
Integer Transform based
Embedding Algorithm
Input: Cover image having m×n pixels, Watermark
Output: Watermarked image
1: For each consecutive pixel pair of the cover image
2: Compute average and difference by forward integer transform
Θ(mn/2) = Θ(mn)
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transform
3: End
4: For each consecutive pixel pair of the cover image
5: Embed next watermark bit into its difference
6: Obtain watermarked pixel pair by reverse integer transform
7: End
Θ(mn/2) = Θ(mn)
Θ(mn)
T = Θ(mn)
Integer Transform based
Extraction Algorithm
Input: Watermarked image having m×n pixels
Output: Retrieved image, Watermark
1: For each consecutive pixel pair of the watermarked image
2: Compute average and difference by forward integer transform
Θ(mn/2) = Θ(mn)
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transform
3: End
4: For each consecutive pixel pair of the cover image
5: Extract next watermark bit from its difference
6: Restore the difference
7: Retrieve original pixel pair by reverse integer transform
8: End
Θ(mn/2) = Θ(mn)
Θ(mn)
T = Θ(mn)
Data Compression based
Embedding AlgorithmInput: Cover image having m×n pixels, Watermark
Output: Watermarked image
1: For each pixel of the cover image
2: Apply L-level quantization to obtain quantized pixel value and quantization remainder
3: EndΘ(mn)
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3: End
4: Losslessly compress the remainders
5: Concatenate the remainders and the watermark to produce the payload
6: For each quantized pixel q of the cover image
7: Obtain s = next L-ary symbol constituting the payload
8: Obtain watermarked pixel p = q + s
9: EndΘ(mn)
T = Θ(mn)
Data Compression based
Extraction AlgorithmInput: Watermarked image having m×n pixels
Output: Retrieved image, Watermark
1: For each pixel of the watermarked image
2: Apply L-level quantization to obtain quantized pixel value and quantization remainder
3: EndΘ(mn)
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3: End
4: Convert the L-ary remainders to the payload bit stream
5: Separate the payload bit stream into the compressed original remainders and the watermark
6: Restore the original remainders by lossless decompression
7: For each quantized pixel q of the watermarked image
8: Retrieve pixel p = q + (next L-ary original remainder)
9: End Θ(mn)
T = Θ(mn)
Histogram Bin Shifting based
Embedding AlgorithmInput: Cover image having m×n pixels, Watermark
Output: Watermarked image
1: Form frequency histogram freq[0..k] of the cover image
/*k is the number of grayscale levels*/
2: Find peak = mode of the frequency histogram
Θ(mn)
Θ(k)
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2: Find peak = mode of the frequency histogram
3: For each pixel p of the cover image
4: If p > peak then p = p+1
5: Else If p = peak then p = p + (next watermark bit)
6: End
7: EndΘ(mn)
T = Θ(mn)+Θ(k) = Θ(mn) [[[[∵∵∵∵k<<mn]]]]
Θ(k)
Histogram Bin Shifting based
Extraction AlgorithmInput: Watermarked image having m×n pixels, peak
Output: Retrieved image, Watermark
1: For each pixel p of the watermarked image
2: If p > peak + 1 then restore p = p − 1
3: Else If p = peak + 1 then
4: Restore p = p − 1
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4: Restore p = p − 1
5: Extract next watermark bit = ‘0’
6: Else If p = peak then extract next watermark bit = ‘1’
7: End
T = Θ(mn)
Pixel Prediction based
Embedding AlgorithmInput: Cover image having m×n pixels, Watermark, Set (SL) of
selected pixel locations for embedding
Output: Watermarked image
1: For each pixel p of the cover image
2: If p belongs to SL then
3: p’ = p interpolated from its neighbors
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3: p’ = p interpolated from its neighbors
4: e = p − p’
5: e’ = sign(e) × {|e| + (next watermark bit)}
6: p = p’ + e’
7: End
8: End
T = Θ(mn)
Pixel Prediction based
Extraction AlgorithmInput: Watermarked image having m×n pixels, Set (SL) of
selected pixel locations for embedding
Output: Retrieved image, Watermark
1: For each pixel p of the cover image
2: If p belongs to SL then
3: p’ = p interpolated from its neighbors
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3: p’ = p interpolated from its neighbors
4: e’ = p − p’
5: Extract next watermark bit = mod(e’,2)
6: Restore e =
7: Restore p = p’ + e
8: End
9: End
T = Θ(mn)
2
e'
Invertible IDCT based
Embedding AlgorithmInput: Cover image having m×n pixels, Watermark, Set (SL) of
locations within an 8×8 block selected for embedding
Output: Watermarked image
1: Divide the cover image into 8×8 blocks
2: For each 8×8 block B
3: X = IDCT of B
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3: X = IDCT of B
4: For each element a of X
5: If location of a Є SL then
6: a = 2 × |a| + (next watermark bit)
7: End
8: End
9: B = Inverse IDCT of (modified) X
10:End
T = Θ(mn)
Invertible IDCT based
Extraction AlgorithmInput: Watermarked image having m×n pixels, Set (SL) of
locations within an 8×8 block selected for embedding
Output: Retrieved image, Watermark
1: Divide the watermarked image into 8×8 blocks
2: For each 8×8 block B
3: X = IDCT of B
4: For each element a of X
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4: For each element a of X
5: If location of a Є SL then
6: Extract next watermark bit = mod(a,2)
7: Restore x =
8: End
9: End
10: Retrieve B = Inverse IDCT of (restored) X
11:End
T = Θ(mn)
2
x
Time Complexities of Reversible
Watermarking Algorithms
� Algorithms belonging to the existing five broad classes of
reversible watermarking have a time complexity of Θ(mn)
� However in practice certain operations specific to some of the
classes involve complex mathematical steps, therefore they have
high runtime requirements
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high runtime requirements
� For example IDCT
Future Research Directions
� Improving the efficiency of reversible watermarking algorithms in
terms of cover data distortion and embedding capacity
� Theoretic analysis of embedding capacity bounds and cover data
distortion characteristics of reversible watermarking algorithms
� Implementation of reversible watermarking algorithms on
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� Implementation of reversible watermarking algorithms on
hardware to improve the runtime requirements of such algorithms
Bibliography� Cox I.J., Miller M.L., Bloom J.A., Fridrich J. and Kalker T., “Digital Watermarking
and Steganography”, Morgan Kaufmann Publishers, 2008.
� Feng J.B., Lin I.C., Tsai C.S. and Chu Y.P., “Reversible watermarking: current status and key issues”, International Journal of Network Security, vol. 2, no. 3, pp. 161–171, May 2006.
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