Digital Digital WatermarkingWatermarking

By: By: Li YangLi Yang

Nov. 14 , 2003Nov. 14 , 2003

OutlineOutline

• Overview of Digital WatermarkOverview of Digital Watermark

• Information HidingInformation Hiding

• Watermarking TechniquesWatermarking Techniques

• Applications of WatermarkingApplications of Watermarking

• Attacks against WatermarkingAttacks against Watermarking

• ConclusionConclusion

Overview of Digital WatermarkOverview of Digital Watermark

What is Digital Watermark?What is Digital Watermark?

• A set of secondary digital data embedded in A set of secondary digital data embedded in the primary digital media (e.g. digital image, the primary digital media (e.g. digital image, video, and audio).video, and audio).

Why Use Digital Watermark?Why Use Digital Watermark?

• Ownership protectionOwnership protection

• Copy controlCopy control

• AuthenticationAuthentication

• Convey other informationConvey other information

Types of WatermarksTypes of Watermarks

Type of DocumentType of Document

TextText ImageImage AudioAudio VideoVideo

working Domain

Spatial domain

Frequency Domain

InvisibleInvisible VisibleVisible

Human PerceptionHuman Perception

FragileFragileRobustRobust

PrivatePrivate PublicPublic

ApplicationApplication

Source BasedSource Based Destination Destination BasedBased

Desired Characteristics of Desired Characteristics of Visible WatermarksVisible Watermarks

• Be visible but not obscure the cover Be visible but not obscure the cover imageimage

• Spreads in a large or important area of Spreads in a large or important area of the image in order to prevent its deletion the image in order to prevent its deletion by clippingby clipping

• Difficult to remove the watermarkDifficult to remove the watermark

Desired Characteristics of Invisible Desired Characteristics of Invisible Robust WatermarksRobust Watermarks

• Neither be noticeable to the viewer nor Neither be noticeable to the viewer nor should degrade the quality of the contentshould degrade the quality of the content

• Must be robust to common signal distortions and Must be robust to common signal distortions and must be resistant to various intentional tampering must be resistant to various intentional tampering solely intended to remove the watermarksolely intended to remove the watermark

• Retrieval of watermark should unambiguously Retrieval of watermark should unambiguously identify the owneridentify the owner

• Minimize the amount of pixel modification on high Minimize the amount of pixel modification on high quality images and art worksquality images and art works

• Insertion of watermark should require little human Insertion of watermark should require little human intervention or laborintervention or labor

Desired Characteristics of Invisible Fragile Watermarks

• Neither be noticeable to the viewer nor should Neither be noticeable to the viewer nor should degrade the quality of the contentdegrade the quality of the content

• Should be readily modified when image pixels Should be readily modified when image pixels values have been alteredvalues have been altered

• Be secure: not be able to be recover or regenerate Be secure: not be able to be recover or regenerate the watermark after the image is alteredthe watermark after the image is altered

• For high quality images, the amount of individual For high quality images, the amount of individual pixel modification should be as small as possiblepixel modification should be as small as possible

Desired Characteristics of Desired Characteristics of Video WatermarkVideo Watermark

• The presence of watermark should not cause any The presence of watermark should not cause any visible or audible effects on the playback of videovisible or audible effects on the playback of video

• Should not affect the compressibility of the digital Should not affect the compressibility of the digital contentcontent

• Should be detected with high degree of reliability. Should be detected with high degree of reliability. The probability of false detection should be The probability of false detection should be extremely smallextremely small

• Be Robust to various intentional and unintentional Be Robust to various intentional and unintentional attacksattacks

• The detection algorithm should be implemented in The detection algorithm should be implemented in circuitry with small extra costcircuitry with small extra cost

Visible Digital WatermarkVisible Digital Watermark

Invisible watermarkInvisible watermark

Information HidingInformation Hiding

History of Information Hiding

• SteganographySteganography– The art and science of information hiding The art and science of information hiding

so that its presence can not be detectedso that its presence can not be detected– Derived from Greek, means “Cover Derived from Greek, means “Cover

Writing”Writing”

Example:Example:– Wax-covered tablets in ancient GreekWax-covered tablets in ancient Greek– Messenger’s TattooMessenger’s Tattoo– Invisible Ink in WWIIInvisible Ink in WWII– Null Cyphers (unencrypted message)Null Cyphers (unencrypted message)– Digital watermarking & copyrightDigital watermarking & copyright

Digital WatermarkingDigital Watermarking

• Commercial Application Commercial Application of Steganographyof Steganography

• Visible Digital Visible Digital Watermarking is not Watermarking is not Steganography in Steganography in definitiondefinition

• Add copyright Add copyright information to message information to message (can be visible)(can be visible)

• The object of The object of communication is the communication is the covercover

SteganographySteganography

• Theory behind the Theory behind the Digital WatermarkingDigital Watermarking

• Hide very existence Hide very existence of messagesof messages

• The object of The object of communication is communication is the hidden the hidden messagesmessages

vsvs

vs.

SteganographySteganographyCover WritingCover Writing• steganography hides steganography hides

its message so it its message so it cannot be seen cannot be seen (conceals their very (conceals their very existence)existence)

• Steganography’s Steganography’s niche in security is to niche in security is to supplement supplement cryptography, not cryptography, not replace it. replace it.

CryptographyCryptographySecret WritingSecret Writing• cryptography cryptography

scrambles a scrambles a messages so it messages so it cannot be cannot be understoodunderstood

Note:Note: Can Combine the two methods to Can Combine the two methods to obtain obtain double protection.double protection.

Watermarking TechniquesWatermarking Techniques

Basic Watermarking ModelBasic Watermarking Model

Encoding,Encoding,Error correction,Error correction,

modulationmodulation

Payload (P)(n bits)Payload (P)(n bits)

Watermark(W)Watermark(W)Watermark Watermark EmbeddingEmbedding

Watermark Watermark Detection orDetection or ExtractionExtraction

Watermarked Image (I’)Watermarked Image (I’)

Distortions Distortions

AttacksAttacks

Key (K)Key (K)

Possible Corrupted Possible Corrupted marked Image (I’’)marked Image (I’’)

Cover Image (I)Cover Image (I)

E(w,I)=I’E(w,I)=I’

D(I,I’’)=W’D(I,I’’)=W’

xxCCWW

W’W’

cc 11

00C(W,W’)=1 or 0C(W,W’)=1 or 0 xx

Techniques in Digital WatermarkingTechniques in Digital Watermarking

• Spatial Domain TechniquesSpatial Domain Techniques– LSBsLSBs

• Frequency Domain TechniquesFrequency Domain Techniques– DCT,FFTDCT,FFT

• Wavelet Domain TechniquesWavelet Domain Techniques– DWTDWT

Spatial Domain: Least-Significant-Bits

• Manipulating Manipulating LLeast-east-SSignificant-ignificant-BBits(LSBs)its(LSBs)

– To hide information in the least-significant To hide information in the least-significant bits of a source imagebits of a source image

• Goal: hide image B in image AGoal: hide image B in image A

LSB cont’d

24-bit Image example: 24-bit images use 3 bytes to represent a color value (8 bits = 1

byte)1 pixel = (00100111 11101001 11001000)

red green blue

Embed secret data 1011 pixels = (00100111 11101001 11001000)

Insert 101: (00100111 11101000 11001001) red green blue

Embed image B in Image A by replacing the LSBs in A by Most Significant-Bits in ImageB

LSB Results - Original Pictures

Cover Page Embedded Watermark

To be embedded

The first LSB replaced by The first LSB replaced by first MSBfirst MSB

The 7 LSB replaced by the The 7 LSB replaced by the 7 MSB7 MSB

LSB cont’d

• Simple and quickSimple and quick

• Vulnerable to compression, cropping, and Vulnerable to compression, cropping, and some image processing.some image processing.

• Can be used for Invisible Fragile Can be used for Invisible Fragile Watermark(spatial domain watermarks is that Watermark(spatial domain watermarks is that picture cropping (a common operation of picture cropping (a common operation of image editors) can be used to eliminate the image editors) can be used to eliminate the watermark.)watermark.)

Simple ComparisonsSimple Comparisons

• Spatial Domain WatermarkingSpatial Domain Watermarking– Simple and fastSimple and fast– Vulnerable to compression, cropping, and Vulnerable to compression, cropping, and

some image processingsome image processing

• Frequency Domain WatermarkingFrequency Domain Watermarking– MoreMore robust than Spatial Domain Watermarking robust than Spatial Domain Watermarking

Applications of Digital WatermarkingApplications of Digital Watermarking

Application: Owner IdentificationApplication: Owner Identification

• Enhance copyright protectionEnhance copyright protection

• Indicate ownership originalsIndicate ownership originals– a visible watermark is in the video domain a visible watermark is in the video domain

where CNN and other television networks where CNN and other television networks place their translucent logo at the bottom place their translucent logo at the bottom right of the screen imageright of the screen image

Application: Authentication

• Detect alternation (Authentication)

• Example – Epson’s digital camera with authentication

watermark

Fragile digital watermarkFragile digital watermark

Watermark extraction

PUEEPUEE

TamperedTampered

PUEEPUEE

Application: Traitor TracingApplication: Traitor Tracing

• Digital CinemaDigital Cinema

Film ServerFilm Server

Cinema #1Cinema #1

Cinema #2Cinema #2

Cinema #nCinema #n

Copy #1Copy #1

With digital watermark #1With digital watermark #1

Copy #2Copy #2

With digital watermark #2With digital watermark #2

Copy #nCopy #n

With digital watermark #nWith digital watermark #n

Distribute Protected FilmsDistribute Protected Films

Application:Broadcast MonitoringApplication:Broadcast Monitoring• Enables content owner and distributors to track the Enables content owner and distributors to track the

dissemination of their contentdissemination of their content– Embedded with a unique identifier , distributor, date, Embedded with a unique identifier , distributor, date,

time informationtime information

– Detectors are placed in major markets, where Detectors are placed in major markets, where broadcasts are received and processedbroadcasts are received and processed

– The digital watermark is decoded and used to The digital watermark is decoded and used to reference a database,resulting in reports to the reference a database,resulting in reports to the owner or distributor that the content has been played owner or distributor that the content has been played in the given market, at a given time, and wether in a in the given market, at a given time, and wether in a full-length.full-length.

– A related db links the content identification to the A related db links the content identification to the content owner, and the distributor identification to content owner, and the distributor identification to the content aggregator, or service provider for the content aggregator, or service provider for broadcast video, as well as distributor or retailer for broadcast video, as well as distributor or retailer for recorded media. Currently in radio, TV, future: recorded media. Currently in radio, TV, future: multicast streams.multicast streams.

Watermarks AttacksWatermarks Attacks

What is watermark attack ? What is watermark attack ?

Intensionally obliterate watermarksIntensionally obliterate watermarks

• Passive Attack (Detection Attack)Passive Attack (Detection Attack)– Prove the existence of hidden dataProve the existence of hidden data

• Active Attack (Distortion Attack)Active Attack (Distortion Attack)– Forge / remove watermarksForge / remove watermarks– Make watermarks uselessMake watermarks useless

Why Study Attacks?Why Study Attacks?

• Identify watermarking technique weaknessIdentify watermarking technique weakness

• Propose improvement and enhancementPropose improvement and enhancement

Types of AttacksTypes of Attacks• Lossy Compression (JPEG, MPEG)Lossy Compression (JPEG, MPEG)

– Save space but can not maintain the original Save space but can not maintain the original images’ integrityimages’ integrity

• Geometric DistortionsGeometric Distortions– Rotation, Scaling, and CroppingRotation, Scaling, and Cropping

• Common Signal ProcessingCommon Signal Processing– Addition noiseAddition noise

• Other Intentional AttacksOther Intentional Attacks– Mosaic AttackMosaic Attack– StirMark AttackStirMark Attack

SDMI and its Public ChallengeSDMI and its Public Challenge

• Secure Digital Music InitiativeSecure Digital Music Initiative– A consortium or forum aiming at protecting the A consortium or forum aiming at protecting the

playing, storing and distributing digital musicplaying, storing and distributing digital music

– 200+ companies/organizations worldwide200+ companies/organizations worldwide• Recording industry, consumer electronicsRecording industry, consumer electronics• Information/secures technology & Internet service Information/secures technology & Internet service

providersproviders

– Pursue “robust & secure” audio watermarking or Pursue “robust & secure” audio watermarking or access and copy controlaccess and copy control

Conclusion

• Digital watermarking is being used in Digital watermarking is being used in many Industries such as the Digital many Industries such as the Digital Multimedia. Multimedia.

• More enhancements are being under More enhancements are being under research around the World to provide us research around the World to provide us with higher information security in the with higher information security in the near future.near future.

Any Questions?Any Questions?