Waterm Tut

8/8/2019 Waterm Tut

1/29

8/8/2019 Waterm Tut

2/29

Example:LSB Encoding

Original Image Watermark

8/8/2019 Waterm Tut

3/29

Replace 4 and 7 LSBs of Original

4 LSBs Watermarked 7 LSBs Watermarked

8/8/2019 Waterm Tut

4/29

What is a Watermark?

A watermark is a secret message that is embedded

into a cover (original or host) message.

Only the knowledge of a secret key allows us toextract the watermark from the cover message.

Effectiveness of a watermarking algorithm is a

function of its

Resilience to attacks.

Capacity.

Stealth.

8/8/2019 Waterm Tut

5/29

What Can Be Watermarked?

Multimedia data.

Video.

Audio. Still Images.

Documents.

Software.

Hardware designs.

8/8/2019 Waterm Tut

6/29

8/8/2019 Waterm Tut

7/29

Watermark Applications

Proof of ownership. Prove ownership in a court of law.

Simple copyright notice may not help for digitalmultimedia data. Easily destroyed.

Copy prevention or control. Recording device may inhibit recording a signal if

detected watermark indicates that it is prohibited.

DVD video and digital music distribution.

Content protection (visible watermarks). Destruction of watermark destroys the content.

8/8/2019 Waterm Tut

8/29


Authentication. Detect if image/video has been altered.

Digital cameras.

Media Bridging. Bridge media such as magazines and the Internet.

Digimarc.

Broadcast Monitoring. Keep track of when and where an advertisementis played.

ConfirMedia from Verance.

8/8/2019 Waterm Tut

9/29


Fingerprinting. Identify the source of an illegal copy.

Unique watermark embedded in each copy.

DiVX, a modified version of DVD.

Secret Communications.

Hide information such that general public do not

know its presence.

Bin Laden hides attack plans in images on the

web USA Today, Feb. 26, 2001.

8/8/2019 Waterm Tut

10/29

Requirements

Requirements vary with application. For

example:

Perceptually transparent - must not perceptuallydegrade original content.

Robust - survive accidental or malicious attempts

at removal.

O

blivious or Non-oblivious - Recoverable with orwithout access to original.

Capacity Number of watermark bits embedded.

Efficient encoding and/or decoding.

8/8/2019 Waterm Tut

11/29

Contradicting Requirements

Perceptual Transparency

Oblivious vs. Non-Oblivious

RobustnessPayload Security

8/8/2019 Waterm Tut

12/29

Example: Additive Watermarks

W( , ) : seudo and om attern {-1,0,1}

kMultiply by gain

factork

I( , ) IW( , )

IW(x,y)=I(x,y)+k W(x,y)

W(x,y) detected

T p

' ( , ) ( , )W

I x y W x yR T" p

No W(x,y) detected

8/8/2019 Waterm Tut

13/29

h

v

Additive watermarks in transformdomain: Spread Spectrum

8/8/2019 Waterm Tut

14/29

Watermark Attacks

Active Attacks.

Hacker attempts to remove or destroy the

watermark. Watermark detector unable to detect watermark.

Key issue in proof of ownership, fingerprinting,

copy control.

Not serious for authentication or covertcommunication.

8/8/2019 Waterm Tut

15/29

Watermark Attacks

Passive Attacks. Hacker tries to find if a watermark is present.

Removal of watermark is not an aim. Serious for covert communications.

Collusion Attacks. Hacker uses several copies of watermarked data

(images, video etc.) to construct a copy with nowatermark.

Uses several copies to find the watermark.

Serious for fingerprinting applications.

8/8/2019 Waterm Tut

16/29

Watermark Attacks

Forgery Attacks.

Hacker tries to embed a valid watermark.

Serious in authentication. If hacker embeds a valid authentication

watermark, watermark detector can accept bogus

or modified media.

8/8/2019 Waterm Tut

17/29

Example: Forging Photo I.D.

Bad

Forgery!

Millionaire with

Swiss bank

account

Assistant

Professor

Thanks

Hong Man,

for this

picture!

8/8/2019 Waterm Tut

18/29

Content-based Watermarking

Original Watermark

8/8/2019 Waterm Tut

19/29

JPEG Compression Attack

8/8/2019 Waterm Tut

20/29

Watermarking Research

Information Theoretic Issues. Compute watermarking capacity

How many watermark bits can be hidden in awatermark channel ?

Capacity when multiple watermarks are used.

Decision Theoretic Issues. Robust watermark detector.

Quickest possible watermark detection.

Invariant to statistical uncertainties.

Achieves desired false alarm and detectionprobabilities.

8/8/2019 Waterm Tut

21/29

Watermarking Research

Signal Processing Issues. What transforms to use ? wavelet, DCT etc.

Geometric invariant transform scale, translation,

and rotation invariance. Watermarking protocols and system issues.

Protocol used by sender and receiver for securetransmission.

Steganalysis. How to analyze multimedia data for the presence

of watermark(s).

Secure Digital Music Initiative (SDMI) has beenhacked!

8/8/2019 Waterm Tut

22/29

Robust Watermarking Techniques- A Communications Framework

+

Media Carrier

HVS

Watermark

Media Carrier

Noise/Attack Channel

Water-

mark

Coding and

Modulation

Decoding and

DemodulationX

8/8/2019 Waterm Tut

23/29

Techniques Developed at

MSyNC Lab

(some results are in collaboration with

Iowa State U. and Polytechnic U.)

8/8/2019 Waterm Tut

24/29

Information TheoreticFormulation

A new watermark channel model. Multiplicative and additive attacks.

Models geometric attacks (killer attack).

Attack parameters assumed imperfectlyknown.

Lower and upper bounds on watermarkingcapacity.

Many current capacity estimates are specificcases of proposed estimates.

Capacity in the presence of multiplewatermarks using multiuser information

theory.

8/8/2019 Waterm Tut

25/29

Multiple DescriptionWatermarking

A new framework for watermarking using

multiple description codes.

Partition the source into multiple descriptions. Each description carries enough information.

Allocate watermarking bits to descriptions subject

to distortion constraints.

Experiments for secure wireless mediatransmission is promising.

Rate-distortion theory formulation.

8/8/2019 Waterm Tut

26/29

Decision Theoretic Formulation

How many pixels to watermark ?

A new measure for watermarking capacity.

Different from standard information theoreticformulation.

Perhaps a more practical measure.

Fast watermark detector.

Computation reduction. Useful for hardware implementation.

8/8/2019 Waterm Tut

27/29

Steganalysis

A distributed detection framework for

analyzing images for presence of

watermarks. Theoretical formulation and practical

algorithm for steganalysis of LSB based

image watermarking.

A new watermarking capacity measure calledsteganographic capacity.

8/8/2019 Waterm Tut

28/29

Projected Applications ofProposed Techniques

Secure media streaming.

Wireless multimedia security.

Watermark error resilience coding.

Error concealment for wireless multimedia

transmission. Refer to

http://www.ece.stevens-tech.edu/~mouli/msync/index.html

8/8/2019 Waterm Tut

29/29

Million Dollar Question

Watermarking or Encryption or Combination?