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Watermarking and Rights Protection
博士班 林秀慧
Outline
Watermarking Background
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Digital Watermark
A digital watermark
a digital signal or pattern imposed on a digital docu
ment ( text, audio,image, video)
visible watermark
the more obvious means of discouraging unauthorized use
by reducing the commercial value of a document
invisible watermark
the watermark is imperceptible to the human eye
when the ownership of data is in question, the watermark
Importance of Digital Watermarking
The sudden increase in watermarking interest is most likely due to the increase in concern over copyright protection of content
copyright-protected digital contents are easily recorded and distributed due to:
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Technologies to protect digital
contents
Cryptography is the most common method of
protecting digital content and is one of the best developed science.
However, encryption cannot help the seller
monitor how a legitimate customer handles the content after decryption.
Digital watermarking can protect content even
after it is decrypted.
Encryption ? Decryption
Applications of Digital Watermarking
Copyright protection (Proof of Ownership)
Fingerprinting (Transaction tracking)
Copy protection (Copy Control)
Data authentication
etc
Broadcast monitoring
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Copyright Protection (Proof of
Ownership)
Using watermarks to provide evidence in
ownership disputes.
1996, Craver et. al. “Can invisible watermarks
solve rightful ownerships?” points out the
counterfeit attacks and a cryptographic solution.
With properly designs, it is technically possible to
prove ownerships with watermarks.
Transaction Tracking
(Fingerprinting)
Using watermarks to identify people who obtain content legall y but illegally redistribute it.
Large scale use for transaction tracking is vulnerable for collu sion attacks, but it is still worthwhile to catch adversaries who lacked the diligence or knowledge to perform these attacks.
Example: the defunct DiVX player
The DIVX Corporation sold a enhanced DVD player that implements a
pay-per-view model.
Each player will place a unique watermark in the video disk it played. Once the video disk is recorded and sold, the adversary can be tracked!
Small-scale transaction tracking where collusion attacks is im possible can be implemented with high security
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Copy Control
Using watermarks to tell recording equipment what
content may not be recorded.
One substantial non-technical problem
It is hard to persuading manufacturers to include watermark
decoders in decoding devices Adding cost
Reduce the value
Solution
Keep honest people honest
Compliant player
Non-Compliant player Legal, encrypted copy
Illegal, decrypted copy
Compliant recorder Compliant recorder Playback control by encryption Copy control by watermarking
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Data Authentication
Embedding signature information in content that c
an be later checked to verify it has not been tamp ered with.
Fragile watermarks
A mark likely to become undetectable after a Work is m
odified in any way. eq. LSB
Embedded signatures
the authentication signature of an image is produced by
a “trustworthy cameras”
the authentication signature is embedded as either a ro
etc
Broadcast Monitoring
Identifying when and where Works are
broadcast by recognizing watermarks embedded in them.
Device Control
Using watermarks to make devices, such as
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Requirements of Digital
Watermarking
Robustness
The ability of the watermark to survive normal processing of content Perceptual Transparency
The perceptual quality of watermarked content Payload
The amount of information that can be carried in a watermark
Oblivious (public, bind) vs. non-oblivous (private, informed) Whether the watermark detector can detect a watermark without the
original content
Security
The ability of the watermark to resists hostile attacks etc
False positive rate
Mutual Dependencies between
the Basic Requirements
Tradeoff
Lossy Compression Watermarking
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Spread Spectrum Watermarking
Original Image
1.Full-frame FFT/DCT
For the largest 1000 A C coef, set 2. Watermark Watermarked Image 3.Inverse FFT/DCT W = w1,...,wn wi: N(0,1) Noise-like X= {x1,...,Xn} 1.FFT/DCT Original Image Received Image Original Watermark Extracted Watermark - Y= {y1,...,yn} T * * * * w w w w ) w 3.sim(w,
Watermark Insertion Watermark Extraction
) 1 ( * i i i x y w ) 1 ( i i i x w x
Construction Example
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Watermarking and Rights Protection
Copyright protection
Embed owner’ watermark
Fingerprinting
Decoding Tests for Ownership
Determination
If Bob obtained Alice’s watermarked image
and introduced his own watermark into it, th en both it leads to case 3
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Rightful Ownership Problem
A B A X W W W X X B W X X
=> Both Alice’s original and watermarked image contains Bob’s watermark
Non-invertible Watermarking
Schemes
Non-invertibility
It is computationally impossible for an attacker to find a
pair of a faked image and a watermark such that the pair can result in the same watermarked image.
Invertible watermarking schemes cannot resolve the
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Customer’s Rights Problems
- Example 1
How can Alice prove that Bob is responsible
Customer’s Rights Problems
- Example 2
How can Eve protect his right and prove his
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Customer’s Rights Problems
TTP Watermarking Protocol
TTP can make sure that each distributed copy has a unique watermark in it TTP keeps purchasing records for every user
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Buyer-Seller Watermarking Protocol
To irrevocably bind the customer to the specific
copy sold to him (for problem in Example 1)
The seller does not know the buyer’s watermark.
The seller does not get to know the exact watermarked
copy that the buyer receives.
The buyer does not know the exact watermark
embedded in the content.
Four subprotocols
Watermark generation, watermark insertion, copyright
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RSA
Public Key Cryptosystem
)) ( ( ) ( mod )) ( ( )) ( (X W X W n E X E W E B B B B K K K K
The Watermark Generation
Protocol
C generates a random but valid watermark W for Bob
after verifying Bob’s certificates of identity
C encrypts W with Bob’s public key, and a digital
signature is also generated
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The Copyright Violator
Identification Protocol
Xˆ
) ( ˆ X W X ) ( ) (X V W UY
Is U in TableX ? protocol fails ! no yes Bob’s ID, , D(X,Y) Unauthorized copy Transaction watermark Bob’s double-watermarked content ), (W E B K SignC(EkB(W))D(X,Y) : extraction algorithm for transaction watermark V For robust watermarking:
Correlating U with every watermar k V in TableX,
Selecting the highest correlation b eyond a confidence threshold.
The Dispute Resolution Protocol
In case Bob denies
Alice can reveal σand and to the judge. The judge first verifies
Judge asks Bob for his “Private Key” to compute W and c
heck for the presence of σ(w) in Y.
The judge can then run the watermark extraction algorit
hm on Y and check if σ(w) is indeed present in Y.
If σ(w) is found in Y, Bob is found guilty otherwise Bob is
innocent. w EKB Sign
E w
B K C
E w
Sign B K C31
Example 4
How to support hierarchical selling channel ?
Buyer Distributor Seller
3. E Kd (X′ σ⊕ s(Wd)) 4. E Kb (X’’ σ⊕ d(Wb)) 1. E Kb (Wb), Signc(E Kb (Wb)) 2. E Kd (Wd), Signc(E Kd (Wd)) X’ = X V⊕ d X’’ = {X ⊕Vd σ⊕ s(Wd)} ⊕ Vb ={X ⊕Vd σ⊕ s(Wd)} ⊕ Vb ⊕σd(Wb)
- 2 more watermarks embeded !
Buyer-Reseller Watermarking
Protocol
Provide rights protection over a second-hand
market (resell)
Support the change of ownership
Relax the requirement of the confidentiality of
encrypted watermarks
Four subprotocols
Watermark generation, watermark insertion, copyright
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Example 5
Nobody can be blamed for distributing the unauthorized copies ! Watermark certificate:
The content may be severely corrupted !
,
,
} , {K E w Sign K E w B B C B K K BBuyer-Reseller Watermarking
Protocol
Content distributor is always involved
Alice may still keep her copy after transfer
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Conclusion
Trusted Third Property plays an important role
Cryptography can be used to compliment watermarking
There is not any protocol that can solve all the problems at
the same time
The buyer-seller protocol is the most suitable for online
e-business
There is a large room and a strong need for developing
effective and fair watermarking protocols for copyright protection
More contents to be protected by watermarks
Software
IP in IC design
Watermarking is a core technology for Digital Rights