DIGITAL WATERMARKING

Key Points• What is

Watermark

• How its Works

• Types of Watermark

• Techniques• Application

Digital Watermarking

Attacking Function

Detecting and

Retrieving Function

Signal

Any Embedding Function ‘E’

Signal

What is

.

FramingSpectral Analysis

DC Carrier Removal

Watermark Addition

Original Signal

Watermarked Signal

Encoding

Framing

Spectral Analysis

Watermark Processing

Watermarked Signal

Original Signal

Decoding

Classification

• Visibleo A visible translucent

image which is overlaid on the primary image

Types of Watermarks

Visible Invisible Robust

InvisibleAn overlaid image which cannot be seen, but which can be detected algorithmically

Classification

Visible Watermark • Any text or logo to verify or hide

content

Fw

• Watermarked Image

a

• constant 0<= α<=1 (If 0, no watermark or if 1, watermark is present)

F• original image

w• watermark

Fw=(1-α)F+ α*W [12]

Classification

Invisible Watermark • Hidden in the signal or content. Cannot be

perceived by human eye or ear. Usually used for authentication or security

• Robust: Cannot be manipulated without disturbing the host signal.

Classification

Robust Watermark

• Spatial domain: In this technique randomly selected subsets are modified. It is not reliable when subjected to filtering or lossy compressions

-LSB coding

-Correlation based-Predictive coding-Patchwork

Techniques and Schemes

a[i] b[i]

A B

∑a[i]-b[i]=2N for watermarked image

0 ,other wise

where N≥1

Correlation based:-Iw(x,y)=I(x,y)+ K * W(x,y)  

Iw(x,y) =  Watermarked image

I(x,y)=Original imagek=gain factor

• Frequency domain: Values of lower frequency coefficients are altered. This technique is applied to the whole image.

- Discrete cosine transform (DCT)- Discrete wavelet transform (DWT)

Techniques and Schemes

Applications?

Ownership assertion

Fingerprinting

Authentication and integrity

Content labeling

Usage control

Content protection

• Basic• Presentation• Interpretation• Implementation• Removal• Geometrical• Wavelet Based

- Active- Passive- Collusion

Attacks

THANK YOUQUESTIONS & SUGGESTIONS