by : vladimir novikov. digital watermarking? allows users to embed special pattern or some data into...

By: Vladimir Novikov

Digital Watermarking?

Allows users to embed SPECIAL PATTERN or SOME DATA into digital contents without changing its perceptual quality.

When data is embedded, it is not written at HEADER PART but embedded directly into digital media itself by changing media contents data

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

Features of Watermarking Invisible/Inaudible

Information is embedded without digital content degradation, because of the level of embedding operation is too small for human to notice the change.

Inseparable The embedded information can survive after

some processing, compression and format transformation.

Unchanging data file size Data size of the media is not changed before

and after embedding operation because information is embedded directly into the media.

How It Works

CLASSIFICATION OF WATERMARK

According to Human Perception Invisible Visible

According to Robustness Fragile Semi fragile Robust

According to types of Document Text Image Audio Video

CLASSIFICATION BY“HUMAN PERCEPTION”

Visible Watermark Logo or seal of the organization which holds

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

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

Visible Watermark

Watermark

Image with watermark

Invisible Watermark

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

AuthenticationCopyrightingEtc…

Invisible Watermark

CLASSIFICATION BY “ROBUSTNESS”

Fragile/Semi Fragile/Robust

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

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

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

CLASSIFICATION BY “DOCUMENT”

Text/Image/Audio watermarking

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

Video Watermarking

Algorithm for video watermarkingDFTDCTDWT

Watermarking in I-frame.

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

Discrete Cosine Transformation

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

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

Remember that JPEG breaks an image into 8x8 unitsSo for DCT n = 8For example:256 gray-scale image each pixel is stored as a value between 0 – 2550 = black pixel255 = white pixelValue between are shades of gray

Wave Transforms

Frequency

Am

plit

ude

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: 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 Video(DCT)

Frequency Domain

Watermarking signal to embed

Host signal

Frequency components(using DCT)

Embedding

Extraction

NvvvV ,...,, 10

NxxxX ,...,, 10

NfffF ,...,, 10

iii xff

iii ffx

if= watermared singal

Purpose of Watermarking

Copyright Protection Fingerprinting Copy Protection Broadcasting Monitoring Data Authentication