Watermarking and Rights Protection

54  Download (0)

全文

(1)

1

Watermarking and Rights Protection

博士班 林秀慧

(2)

Outline

Watermarking Background

(3)

3

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

(4)

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:

(5)

5

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

(6)

Applications of Digital Watermarking

Copyright protection (Proof of Ownership)

Fingerprinting (Transaction tracking)

Copy protection (Copy Control)

Data authentication

etc

 Broadcast monitoring

(7)

7

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.

(8)

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

(9)

9

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

(10)

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

(11)

11

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

(12)

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

(13)

13

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

(14)

Mutual Dependencies between

the Basic Requirements

Tradeoff

Lossy Compression Watermarking

(15)

15

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  

(16)

Construction Example

(17)

17

Watermarking and Rights Protection

Copyright protection

 Embed owner’ watermark

Fingerprinting

(18)

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

(19)

19

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

(20)

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

(21)

21

Customer’s Rights Problems

- Example 1

 How can Alice prove that Bob is responsible

(22)

Customer’s Rights Problems

- Example 2

 How can Eve protect his right and prove his

(23)

23

Customer’s Rights Problems

(24)

TTP Watermarking Protocol

 TTP can make sure that each distributed copy has a unique watermark in it  TTP keeps purchasing records for every user

(25)

25

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

(26)
(27)

27

RSA

Public Key Cryptosystem

)) ( ( ) ( mod )) ( ( )) ( (X W X W n E X E W E B B B B K K K K       

(28)

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

(29)

29

The Copyright Violator

Identification Protocol

) ( ˆ X W X   ) ( ) (XV  WU

Y

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.

(30)

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 C

(31)

31

Example 4

How to support hierarchical selling channel ?

Buyer Distributor Seller

3. E Kd (X′ σs(Wd)) 4. E Kb (X’’ σd(Wb)) 1. E Kb (Wb), Signc(E Kb (Wb)) 2. E Kd (Wd), Signc(E Kd (Wd)) X’ = X Vd X’’ = {X ⊕Vd σs(Wd)} ⊕ Vb ={X ⊕Vd σs(Wd)} ⊕ Vb σd(Wb)

- 2 more watermarks embeded !

(32)

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

(33)

33

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 B

(34)

Buyer-Reseller Watermarking

Protocol

Content distributor is always involved

Alice may still keep her copy after transfer

(35)

35

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

數據

Updating...

參考文獻