Digital Watermarking

Digital Digital WatermarkingWatermarking

a Multimedia Security. . .a Multimedia Security. . .

PRESENTED BY-RAJIV RANJAN KR.

Digital Watermarking?Digital Watermarking?

Allows users to embed Allows users to embed SPECIAL PATTERN SPECIAL PATTERN or or SOME SOME

DATA DATA into digital contents without changing its into digital contents without changing its perceptual quality.perceptual quality.

When data is embedded, it is not written at When data is embedded, it is not written at HEADER HEADER

PART PART but embedded directly into digital media itself but embedded directly into digital media itself by changing media contents databy changing media contents data

Watermarking is a key process for the Watermarking is a key process for the PROTECTIONPROTECTION of copyright of copyright ownership of electronic data.ownership of electronic data.

Features of Features of WatermarkingWatermarking

Invisible/InaudibleInvisible/Inaudible Information is embedded without digital content Information is embedded without digital content

degradation, because of the level of embedding degradation, because of the level of embedding operation is too small for human to notice the change. operation is too small for human to notice the change.

InseparableInseparable The embedded information can survive after some The embedded information can survive after some

processing, compression and format transformation.processing, compression and format transformation. Unchanging data file sizeUnchanging data file size

Data size of the media is not changed before and after Data size of the media is not changed before and after embedding operation because information is embedded embedding operation because information is embedded directly into the media.directly into the media.

How It WorksHow It Works

CLASSIFICATION OF CLASSIFICATION OF WATERMARKWATERMARK

According to According to Human PerceptionHuman Perception (a)invisible(b)visible(a)invisible(b)visible

According to According to RobustnessRobustness (a)fragile(b)semi fragile(c)robust(a)fragile(b)semi fragile(c)robust

According to types of According to types of DocumentDocument (a)text(b)image(c)audio(d)video(a)text(b)image(c)audio(d)video

CLASSIFICATION BYCLASSIFICATION BY“HUMAN “HUMAN

PERCEPTION”PERCEPTION”

Visible WatermarkVisible Watermark Logo or seal of the organization which holds the Logo or seal of the organization which holds the

rights to the primary image, it allows the primary rights to the primary image, it allows the primary image to be viewed, but still visible it clearly as the image to be viewed, but still visible it clearly as the property of the owning organization.property of the owning organization.

Overlay the watermark in such a way that makes it Overlay the watermark in such a way that makes it difficult to remove, if the goal of indicating property difficult to remove, if the goal of indicating property rights is to be achieved. rights is to be achieved.

Visible WatermarkVisible Watermark

Invisible WatermarkInvisible Watermark

Embedding level is too small to noticeEmbedding level is too small to notice Can be retrieved by extraction softwareCan be retrieved by extraction software Applications:Applications:

AuthenticationAuthentication CopyrightingCopyrighting Etc…Etc…

Invisible WatermarkInvisible Watermark

CLASSIFICATION BY CLASSIFICATION BY “ROBUSTNESS”“ROBUSTNESS”

Fragile/SemiFragile/RobustFragile/SemiFragile/Robust

A watermark is called A watermark is called fragilefragile if it fails to be if it fails to be detected after the slightest modification.detected after the slightest modification.

A watermark is called A watermark is called semi-fragilesemi-fragile if it resists if it resists begining transformations but fails detection begining transformations but fails detection after malignant transformations.after malignant transformations.

A watermark is called A watermark is called robustrobust if it resists a if it resists a designated class of transformations.designated class of transformations.

CLASSIFICATION BY CLASSIFICATION BY “DOCUMENT”“DOCUMENT”

Text/Image/Audio watermarkingText/Image/Audio watermarking

Text/Image/Audio watermarking refers to Text/Image/Audio watermarking refers to embedding watermarks in an text/image/audio embedding watermarks in an text/image/audio in order to protect the image from illegal in order to protect the image from illegal copying and identify manipulation.copying and identify manipulation.

Video WatermarkingVideo Watermarking

Algorithm for video watermarking DFT DCT DWT

Watermarking in I-frame.

Video watermarking refers to embedding watermarks in Video watermarking refers to embedding watermarks in a video sequence in order to protect the video from a video sequence in order to protect the video from illegal copying and identify manipulationillegal copying and identify manipulation

Discrete Cosine Discrete Cosine TransformationTransformation

DCT convert images from DCT convert images from spatial-domainspatial-domain to to frequency-frequency-domaindomain to decorrelate pixels to decorrelate pixels

The discrete cosine transform (DCT) helps to separate the The discrete cosine transform (DCT) helps to separate the image into parts of differing importance (with respect to the image into parts of differing importance (with respect to the image's visual quality). The DCT is similar to the discrete image's visual quality). The DCT is similar to the discrete Fourier transformFourier transform

Remember that JPEG breaks an image into 8x8 unitsSo for DCT n = 8

For example256 gray-scale image each pixel is stored as a value between 0 – 2550 = black pixel255 = white pixelValue between are shades of gray

Wave TransformsWave Transforms

Frequency

Am

plit

ude

DCT: One Dimensional DCT: One Dimensional

where

1

0

)(2

)12(cos

2)( )(

n

i

ifn

uip

nuF i

n = total no. of data item

p = pixel

F = coefficients

f(i)= is the intensity of the i th pixel

The general equation for a 1D (n data items) DCT is defined by the following equation:

DCT: 2DDCT: 2D

),(2

)12(cos

2

)12(cos

22),(

1

0

1

0

)()(

jifm

vj

n

uipp

mnvuF

n

i

m

j

ji

•The input image is of size n by m;

•f(i,j) is the intensity of the pixel in row i and column j;

•F(u,v) is the DCT coefficient in row k1 and column k2 of the DCT matrix.

The general equation for a 2D (N by M image) DCT is defined by the following equation:

Watermarking in Watermarking in Video(DCT)Video(DCT)

Frequency DomainFrequency Domain

Watermarking signal to embedWatermarking signal to embed

Host signalHost signal

Frequency components(using DCT)Frequency components(using DCT)

EmbeddingEmbedding

ExtractionExtraction

NvvvV ,...,, 10

NxxxX ,...,, 10

NfffF ,...,, 10

iii xff

iii ffx

if = watermared singal

Purpose of WatermarkingPurpose of Watermarking

Copyright ProtectionCopyright Protection FingerprintingFingerprinting Copy ProtectionCopy Protection Broadcasting MonitoringBroadcasting Monitoring Data AuthenticationData Authentication

Thank you !!!Thank you !!!