디지털 컨텐츠 보호 기술 ( 워터마킹 ) 동향 2000. 10. 27. 오 황 석 Hsoh@etri.re.kr...

디지털 컨텐츠 보호 기술 ( 워터마킹 ) 동향

2000. 10. 27.

오 황 석

Hsoh@etri.re.kr가상현실연구개발센터한국전자통신연구원

차 례개요분류요구 사항공격응용 분야동향Image watermarking

Video watermarking

요약

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서론 (1)

▣ Digital technologies present new threats for IPs and contents :◈ Easy access to information◈ Modification/falsification facilities◈ Redistribution facilities◈ Perfect copies

▣ Methods that prevent unauthorized access to copyrighted digital contents are required in wide ranges of applications

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서론 (2)

▣ Two methods for copyright protection◈ Cryptography

– Transform digital contents into unperceivable format– Encryption/Decryption

◈ Watermarking– Hide the copyright control information into digital content by

modification the content itself

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워터마킹 개요 (1)

▣ Definition◈ Technique for embedding information into digital contents◈ Visible watermark

– Alter perceptual quality of original contents– Analogous to watermark found on paper

◈ Transparent watermark– Does not alter perceptual quality of content– Watermark is hidden– Steganography(covered writing)

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워터마킹 개요 (2)

▣ Steganography vs. Watermarking ◈ Steganography

– Covert point-to-point communication between two parties– Interpreted to means of information hiding in other information– Example : sending a message to a spy by marking certain letters

in a newspapers using invisible ink

◈ Watermarking– Has the additional requirement of robustness against possible

attacks

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워터마킹 개요 (3)

▣ Generic watermark embedding scheme

▣ Generic watermark recovery scheme

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워터마킹 역사▣ Watermarks are used to keep track of paper provenance and thus format

and quality identification in the art of handmade papermaking nearly 700 years ago

▣ The first publication of digital image watermarking was published by Tanaka et al in 1990 and by Caronni and Tirkel et al. in 1993

▣ Now, there are a lot of topics open for further research, practical working methods and systems have been developed

▣ Number of publications on digital watermarking according to INSPEC

Years 1992 1993 1994 1995 1996 1997 1998 1999Publications 2 2 4 13 29 64 103 약250

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워터마킹 분류 (1)

▣ Types of watermarks◈ Watermarks : visible or invisible◈ Verifiability : private or public◈ Watermarking techniques : fragile or robust◈ Key : symmetric or asymmetric◈ Original necessary : yes or no

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워터마킹 기법 분류▣ Spatial-domain techniques▣ Transform-domain techniques

◈ DCT-based◈ Wavelet-based◈ Other transforms

▣ Compressed stream-domain techniques◈ Watermarking MPEG bit streams

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워터마킹 요구 사항 (1)

▣ Perceptual transparency◈ Watermarked content has the same subjective quality as the original

contents▣ Robustness

◈ Nobody is able to remove, alter, or damage the watermark without a secret key

▣ Security◈ Secret key determines the value of watermark and the locations

where the watermark is embedded▣ Payload of the watermark

◈ Amount of information to be embedded▣ Capacity

◈ Multiple watermark can be embedded/extracted

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워터마킹 요구 사항 (2)

▣ Invisibility/robustness and cost are conflicting requirements

Invisibility limits theenergy of watermark

Robustness increase whenwatermark energy increases

Invisibility and robustness require costly processes

Cost rapidly increases with processes complexity

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Levels of Robustness

▣ Spatial-domain watermarks◈ Watermark embedded in lower order bit planes◈ Transparent mark◈ Visually pleasing, not robust to compression

▣ Transform-domain watermarks◈ Watermark added to frequency coefficients◈ Watermark location and strength based on perceptual rules

▣ Watermark insertion based on utilizing formal HVS model in order to provide the strongest watermark while guaranteeing transparency

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워터마킹에 대한 공격▣ 비의도적인 공격

◈ A/D, D/A conversion, resampling◈ Cropping◈ Compression◈ Geometric distortions(Synchronization)◈ Additive noise

▣ 의도적인 공격◈ IBM attack◈ Collusion

▣ 공격을 위한 software◈ UnSign software (http://altern.org/watermark/)◈ StirMark

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워터마킹 활용 분야 (1)

▣ 기술적인 측면에서 활용 분야◈ Copyright and content protection◈ Authentication and integrity verification◈ Digital content tracking◈ Security(e.g. passport photos)◈ Metadata tagging(annotation)◈ Usage control◈ Secret communication◈ And many more

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워터마킹 활용 분야 (2)

▣ 대상 컨텐츠에 따른 활용 분야

Document

WatermarkingTechnology

VOD

Graphics

Audio

Image

Video

Text

InternetMagazineInternet

NewspaperInternet

TV

InternetRadio

EducationMaterial

AOD

Certificates

e-Book

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워터마킹 개발 동향 (1)

▣ 국내 동향◈ 벤처 기업을 중심으로 워터마킹 기술에 대한 연구가 진행 , 독자적인

솔루션 제공◈ 실트로닉스와 ETRI, 마크애니와 삼성에서 공동 연구 결과를

SDMI(Secure Digital Music Initiative) 에 제안하였음◈ 전자부품연구원이 주축이 되어 DMC(Digital Music Consortium,

http://multimedia.kangwon.ac.kr/sdm/index.html) 를 결성하여 MP3 위주의 표준화를 진행 중임

◈ 대학을 중심으로 결성된 ISMC(Information Security in Multimedia, http://multimedia.kangwon.ac.kr/ismc/index.html) 에서는 멀티미디어 컨텐츠 보호용 DTCP(Digital Transmission Copyright Protection)

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워터마킹 개발 동향 (2)▣ 국외 동향

◈ SDMI 를 통하여 디지털 음악의 저작권 보호 및 불법 복제 방지 기술을 위한 표준안을 제정하고 있음

◈ OPIMA(Open platform initiative for multimedia access) 에서는 포괄적인 디지털 컨텐츠 보호를 위한 표준을 정하고 있음

◈ DVD Forum 에서는 DVD 복제 방지를 위한 기술 표준을 제정하고있으며 , IBM 등 4 개 회사는 BMG, EMI 등 5 개 음반회사와 함께 저작권 보호를 위한 DVD 오디오 포맷을 1993 년 3 월에 제정하였음

◈ MPEG 에서는 음반산업 , 영상산업 , 가전제품 메이커를 대표하는 단체 및 기업이 주축을 이루어 MPEG-4 IPMP 에 대한 기술 표준 제정을 하고 있음

◈ 디지털 방송 , 인터넷에서의 프로그램 제작 , 편집 / 전송 및 송출 , 소비의 전 단계에 걸쳐 저작권을 포함한 컨텐츠 정보의 보호 , 전자 상거래와의 접속 등을 위한 MPEG-21(Multimedia Framework) 의 표준화가 1999 년 10 월부터 활동을 시작하여 2001 년 12 월에 기술 보고서 작성을 목표로 하고 있음

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Companies▣ Digimarc

◈ Image watermark ◈ One of the first products ◈ 14 U.S. patents

▣ Bluespike ◈ Giovanni still image watermark

▣ ARIS◈ Audio watermark

▣ MediaSec▣ Signafy▣ Signum▣ Intertrust

◈ DRM

▣ IBM▣ HP▣ NEC

▣ MarkAny▣ Digital-Innotech▣ 실트로닉스▣ 코리아컨텐츠

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관련 사이트▣ Watermarking and data hiding

◈ http://www-nt.e-technik.uni-erlangen.de/~hartung/watermarkinglinks.html

▣ WatermarkingWorld◈ http://www.watermarkingworld.org/

▣ Digital Copyright Protection & Digital Watermarking Technology◈ http://www-sal.cs.uiuc.edu/~l-qiao/watermarking.html

▣ Imprimatur◈ http://www.imprimatur.net

▣ Digimarc’s extractor◈ http://www.digimarc.com

▣ KAIST’s KAIMark◈ http://www.digital-innotech.com

▣ MarkAny’s MAIM◈ http://www.markany.com

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Image Watermarking

Spatial-domain watermarking

Transform-domain watermarking

Perceptual-based watermarking

Object-based watermarking

Robust to JPEG compression

Robust to geometric distortions

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Spatial-domain Watermarking

▣ Van Schyndel et al(1994)◈ Alter least significant bits

▣ Caronni(1995)◈ Low-level geometric patterns

▣ Pitas(1996)◈ Add small luminance value to random set of pixels

▣ Maes and Overveld(1998)◈ Watermark embedded in geometric feature

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Block Mean Approach(1)

▣ An image is divided into blocks▣ The mean of each block may then be incremented to encode

a ‘1’ or decrement to encode a ‘0’(or vice versa) of the ASCII representation of watermark

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Block Mean Approach(2)

▣ Procedure◈ Step 1 : Divide the image into blocks◈ Step 2 : Subtract the mean of the block from each pixel in the

block◈ Step 3 : Normalize pixel values within each block so that they

range between -127 and 127◈ Step 4 : Compute the transform of the image block◈ Step 5 : Modulate selected coefficients of the transformation.

The coefficients that are selected are those that are most relevant to the intelligibility of the image

◈ Step 6 : Compute the inverse transform, denormalize, add the mean to each pixel in the block and replace the image block in the image

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Block Mean Approach(3)

▣ How to select the transformed coefficients◈ Let F(k1, k2) be a transformed coef. Where 0<= k1, k2 <N◈ G(k1,k2) = w(k1, k2)F(k1,k2), where w is weighting factors◈ Select the coefficient that is satisfying the

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Block Mean Approach(4)

▣ Simulation◈ Test image : Lenna 512x512◈ Block size : 12x12◈ Pixels are incremented by 3 to transmit a binary ‘1’ and

decremented by 3 to convey a binary ‘0’.◈ Message : ‘012345 this is a watermark…’◈ Transformation : DCT, Wavelet

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Block Mean Approach(5)

▣ Results

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Block Mean Approach(6)

▣ Results

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Transform-domain Watermarking(1)

▣ Stages of watermark insert and extract

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Transform-domain Watermarking(2)

▣ Description of watermarking procedure◈ Let D is document and V=(v1, v2, … ,vn) is a sequence of value

s extracted from D

◈ Let X=(x1, x2, …,xn) is watermark to be inserted

◈ Let D’ be a watermarked data and D* be attacked data

▣ Insertion of the watermark X into D◈ Insert X into V to obtain V’ as

– v’i = vi + axi

– v’i = vi(1+axi)

– v’i = vi(eaxi)

▣ Choosing the length n

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Transform-domain Watermarking(3)

▣ Extract the watermark and evaluating the similarity◈ Extract the X* from the V* in D*◈ The measure of similarity

– sim(X, X*) = (X X*)/sqrt(XX*)– Decision by considering the sim(X, X*) > Threshold– The detection threshold based on the goal of minimizing false

negatives and minimizing false positives

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Transform Domain Watermarking(4)

▣ Simulation◈ Test image : Bavarian couple◈ Modifying 1000 of the more perceptually significant components

of the image spectrum in DCT domain

◈ Used equation : vi’ = vi(1+axi), a = 0.1

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Transform Domain Watermarking(5)

▣ Uniqueness ◈ Watermarked image and watermark detector response ◈ Detector response : 32.0

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Transform Domain Watermarking(11)

▣ Print, xerox, and scan◈ detector response : 7.0

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Transform Domain Watermarking(12)

▣ Attack by watermarking watermarked images

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Transform Domain Watermarking(13)

▣ Attack by collusion

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Video Watermarking

▣ Can not trivially extend still image approaches◈ Additional attacks are possible◈ Computationally very expensive◈ Compression◈ Real-time applications◈ Spatial masking differs from temporal masking

▣ Unique attacks on video◈ Frame shuffling, insertion, removal◈ Inter-frame collusion◈ A/D conversion◈ NTSC/PAL conversion

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Video Watermarking of MPEG bit streams

▣ Extract quantized DCT block from MPEG bit stream▣ Add watermark to non-zero coefficients in block▣ Requantize and code the altered coefficients▣ Insert coded coefficients into MPEG bit stream▣ To prevent increase in data rate, reject watermarked

coefficients which increase data rate significantly

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Digital Watermarking of Coded Video in the MPEG-2 Bitstream Domain(1)▣ Proposed by Frank Hartung▣ MPEG-2 encoding of one 8x8 block

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Digital Watermarking of Coded Video in the MPEG-2 Bitstream Domain(2)▣ Generic scheme for watermarking of the compressed video

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Digital Watermarking of Coded Video in the MPEG-2 Bitstream Domain(3)▣ Proposed scheme for watermarking of compressed video with drift compens

ation

▣ Retrieval of watermark : compare the watermarked sequence with the original compressed sequence

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MPEG Bitstream Labeling Technique(1)

▣ Re-encoding resistant MPEG labeling technique◈ Each bit out of the label string has its own area in an I-frame

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MPEG Bitstream Labeling Technique(3)

◈ Embedding and extraction of the label

– If label bit “1” must be embedded, the energy in A is removed, ie. EA = 0, then the difference becomes D=-EB

– If label bit “0” must be embedded, the energy in A is removed, ie. Eb = 0, then the difference becomes D=Ea

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Object-based Video Watermarking(1)

▣ Proposed by Swanson▣ Embedding procedure

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Multiresolution Scene-based Video Watermarking▣ Proposed by swanson▣ Diagram of video watermarking

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Summary

▣ Open problems◈ Is digital watermarking the solution for copyright protection?Since no watermarking algorithm resists all the attacks

◈ Is there a better way to solve the problem of intellectual property protection of digital contents?

Nothing

But many research areas related to watermarking must be studied

▣ Reference : contact me without hesitation