디지털 컨텐츠 보호 기술 ( 워터마킹 ) 동향 2000. 10. 27. 오 황 석 [email protected] 가상현실연구개발센터 한국전자통신연구원

디지털 컨텐츠 보호 기술 ( 워터마킹 ) 동향

2000. 10. 27.

오 황 석

[email protected]가상현실연구개발센터한국전자통신연구원

차 례개요분류요구 사항공격응용 분야동향Image watermarking

Video watermarking

요약

Virtual Reality Research and Development Center -3- ETRI Proprietary

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


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


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)



▣ 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



▣ Generic watermark embedding scheme

▣ Generic watermark recovery scheme


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


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


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

◈ DCT-based◈ Wavelet-based◈ Other transforms

▣ Compressed stream-domain techniques◈ Watermarking MPEG bit streams


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


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


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


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


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


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


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)


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


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


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


Image Watermarking

Spatial-domain watermarking

Transform-domain watermarking

Perceptual-based watermarking

Object-based watermarking

Robust to JPEG compression

Robust to geometric distortions


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


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



▣ 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



▣ 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



▣ 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



▣ Results



▣ Results


Transform-domain Watermarking(1)

▣ Stages of watermark insert and extract



▣ 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



▣ 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


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



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



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



▣ Attack by watermarking watermarked images



▣ Attack by collusion


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


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


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


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


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


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


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


Object-based Video Watermarking(1)

▣ Proposed by Swanson▣ Embedding procedure


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


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

Documents

디지털 컨텐츠 보호 기술 ( 워터마킹 ) 동향 2000. 10. 27. 오 황 석 [email protected] 가상현실연구개발센터 한국전자통신연구원