Digital Watermarking

Thái Chí MinhTrần Lương Khiêm

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Content

Introduction History Applications Requirements Techniques Attacks

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Content

Introduction History Applications Requirements Techniques Attacks

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Introduction

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Introduction

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Introduction

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Introduction

Relation between embedded message and cover work

Goal and assumption

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Content

Introduction History Applications Requirements Techniques Attacks

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History

Histiæus & the slave

Paper watermark, 1282

Banknote. 18th century

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History In 1954, Emil Hembrooke of the Muzak Corporation filed a patent for

watermarking” musical Works The first Information Hiding Workshop (IHW) ,which included digital

watermarking as one of its primary topics, was held in 1996

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Content

Introduction History Applications Requirements Techniques Attacks

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Applications

Broadcast monitoring Owner identification Proof of ownership Transaction tracking Content authentication Copy control

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Broadcast monitoring

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Owner identification

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Proof of ownership

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Transaction tracking

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Transaction tracking

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Content authentication

Digital signature is NOT enough

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Content authentication

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Copy control

Cryptography is NOT enough

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Copy control

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Content

Introduction History Applications Requirements Techniques Attacks

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Requirements

Perceptual Transparency Robustness Data payload With / Without originals Security

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Perceptual Transparency

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Robustness

Fragile Semi-fragile Robust

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Data payload

Data payload refers to the number of bits a watermark encodes within a unit of time or within a Work

Different applications may require very different data payloads

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With / Without originals

Non-blind watermarkingType I

Type II

Semi-blind watermarking

Blind watermarking

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Security

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The mutual dependencies among the elements

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Content

Introduction History Applications Requirements Techniques Attacks

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Techniques

LSB Spread spectrum Applying on Vietnamese documents

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Techniques

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Techniques

There are many techniques to do watermarking in digital things:Spatial domain watermarking: LSB, in text

data, …Transform domain watermarking: frequency-

based watermarking, wavelet based watermarking○ Embedding the watermark in the transform

domain from carrier object (using DCT, DFT, DWT, …)

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Techniques

LSB:Embedding:

○ Choosing some representation values (e.g pixels) of carrier object.

○ Embed the bits of message (watermark) to LSBs of representation valueMessage ‘A’: 100 0001Carrier object: RGB (2 bits)

100000 010101 101100

010001 100001 000100

101110 011010 111000

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Techniques

LSB:Embedding:

○ Choosing some representation values (e.g pixels) of carrier object.

○ Embed the bits of message (watermark) to LSBs of representation valueMessage ‘A’: 100 0001Carrier object: RGB (2 bits)

100001 010100 101100

010000 100001 000100

101111 011010 111000

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Techniques

LSB:Detector:

○ Retrieve the watermark by having the knowledge of the representation values (e.g pixels) used for embedding individuals bits

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Techniques

Spread spectrumUsing frequency domain transform to

convert the input image into another domain and embedding the watermark to this domain.

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Techniques

• Apply on Vietnamese documents

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Techniques

• Apply on Vietnamese documents

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Techniques

• Apply on Vietnamese documents○ Besides, we can use some methods:

Vertically shifting text lines Horrizontally shifting words

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Content

Introduction History Applications Requirements Techniques Attacks

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Attacks

From processing From attackers

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Attacks

The actions take effect on the watermark embedded in carrier objects.Affects:

○ Destroying the watermark or modifying the watermark with new wrong information.

○ Removing the watermark entirely.But: not degrading the quality of carrier

objects (image, audio, video)Relating to a requirements of watermarking:

Robustness

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Attacks Classification:

From proscessing carrier objects○ Common signal processing: digital-to-analog and

analog-to-digital conversion, or change image contrast, color, JPEG compression, …

○ Common geometric distortions: scaling, rotating, cropping, dithering …

From attacker○ Mosaic○ Collusion attacks: get the watermark or remove

watermarks entirely to get the original work.○ …

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Attacks

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AttacksMosaic attack

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Attacks How to protect watermarks from attacks

Understanding and applying new researchs in watermarking

Using StirMark Benchmark evaluation engine to evaluate your watermarking scheme○ “All vendors of digital watermarks have their

products benchmarked by Stirmark and as of August 2001, no watermark from any vendor survives the test, ie: the watermarks are all removed without degradation to image quality occurring. “

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