Thái Chí Minh Trần Lương Khiêm 1

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 2

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 3

Introduction 4

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Relation between embedded message and cover work Goal and assumption 7

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 8

History Histiæus & the slave Paper watermark, 1282 Banknote. 18 th century 9

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

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 11

Applications  Broadcast monitoring  Owner identification  Proof of ownership  Transaction tracking  Content authentication  Copy control 12

Broadcast monitoring 13

Owner identification 14

Proof of ownership 15

Transaction tracking 16

Transaction tracking 17

Content authentication  Digital signature is NOT enough 18

Content authentication 19

Copy control  Cryptography is NOT enough 20

Copy control 21

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 22

Requirements  Perceptual Transparency  Robustness  Data payload  With / Without originals  Security 23

Perceptual Transparency 24

Robustness  Fragile  Semi-fragile  Robust 25

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 26

With / Without originals  Non-blind watermarking Type I Type II  Semi-blind watermarking  Blind watermarking 27

Security 28

The mutual dependencies among the elements 29

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 30

Techniques  LSB  Spread spectrum  Applying on Vietnamese documents 31

Techniques 32

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, …) 33

Techniques  LSB: Embedding: ○ Choosing some representation values (e.g pixels) of carrier object. ○ Embed the bits of message (watermark) to LSBs of representation value Message ‘A’: Carrier object: RGB (2 bits)

Techniques  LSB: Embedding: ○ Choosing some representation values (e.g pixels) of carrier object. ○ Embed the bits of message (watermark) to LSBs of representation value Message ‘A’: Carrier object: RGB (2 bits)

Techniques  LSB: Detector: ○ Retrieve the watermark by having the knowledge of the representation values (e.g pixels) used for embedding individuals bits 36

Techniques  Spread spectrum Using frequency domain transform to convert the input image into another domain and embedding the watermark to this domain. 37

Techniques Apply on Vietnamese documents 38

Techniques Apply on Vietnamese documents 39

Techniques Apply on Vietnamese documents ○ Besides, we can use some methods: Vertically shifting text lines Horrizontally shifting words 40

Content  Introduction  History  Applications  Requirements  Techniques  Attacks 41

Attacks  From processing  From attackers 42

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 43

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. ○ … 44

Attacks 45

Attacks Mosaic attack 46

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. “ 47

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