Watermark Description by Ravi Sharma

1. WATERMARKING

2. Content
 What is watermarking
 History
 Digital Watermarking
 Classification
 Visible And Invisible Watermarking
 Text And Image Watermarking
 Examples, Techniques And Applications
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3. What is Watermarking
 A watermark is a recognizable image or
pattern in paper that appears as various shades
of lightness/darkness when viewed by
transmitted light (or when viewed by reflected
light, a top a dark background), caused by
thickness variations in the paper.
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4. Watermarking History
 More than 700 years ago, watermarks were used in Italy to
indicate the paper brand and the mill that produced it.
 By the 18th century watermarks began to be used as
anticounterfeiting measures on money and other documents.
 The term watermark was introduced near the end of the 18th
century.
 It was probably given because the marks resemble the effects
of water on paper
 The first example of a technology similar to digital
watermarking is a patent filed in 1954 by Emil Hembrooke for
identifying music works.
 In 1988, Komatsu and Tominaga appear to be the first to use
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the term “digital watermarking”.

5. Paper Watermarks
Paper Watermarks: Formed during the manufacturing
process of the paper when the paper is wet, so that fibers
can be disturbed according to the design of the watermark.
Used mainly for identification and authentication
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6. Digital Watermarking
Definition: A digital watermark is a digital signal or pattern
inserted into a digital document such as text, graphics or
multimedia, and carries information unique to the copyright
owner, the creator of the document or the authorized
consumer.
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7. Common Examples
 Currency Notes
 Stamps
 Passports
 Legal Documents
 Logos used by cable TV channels
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8. Currency Notes
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9. Watermark Example
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10. Watermark Example
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11. Example
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12. Digital Watermark Classification
 Based on visibility of watermarks
- Visible Watermarks
- Invisible Watermarks
 Based on the content to be watermarked
- Text Watermarking
- Image, Audio, Video Watermarking
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13. Visible Watermarking
 In visible watermarking, the information is
visible in the picture or video.
 Typically, the information is text or a logo
which identifies the owner of the media.
 When a television broadcaster adds its logo to
the corner of transmitted video, this is also a
visible watermark.
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14. Visible Watermarking
+ =
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15. Invisible Watermarking
 In invisible watermarking, information is
added as digital data to audio, picture or video,
but it cannot be perceived as such (although it
may be possible to detect that some amount of
information is hidden).
 It is also possible to use hidden embedded
information as a means of covert
communication between individuals.
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16. Small changes in brightness,
contrast, etc.
(sail_e.jpg): Signed image. Verify
(sail.jpg): Original image. with secret key 100001.
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17. Watermarking Process
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18. Basic Principle
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19. Techniques for Texts
 Text Line Coding: Change the spacing
between lines.
 Word-shift Coding: Change the spacing
between words.
 Character Encoding: Alter the shapes of
characters.
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20. Text line coding example
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21. Word-shift coding example
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22. Techniques for Images
 Spatial Watermarking: Just change some of the
values of the pixels in the lower bit plane; e.g.,
Change some of the bits from 1 to 0 or 0 to 1.
 Frequency Domain Watermarking: First
convert the image to the frequency domain and
then apply the watermark in the low frequency
regions.
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23. Example
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24. Example
Original Watermarked Version
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25. Watermarking Attacks
 Signal enhancement (sharpening, contrast enhancement,
etc.)
 Additive and multiplicative noise (gaussian, uniform, etc.)
 Filtering (High pass, low pass, linear, nonlinear, etc.)
 Lossy compression (JPEG, MPEG-x, H.26x, etc.)
 Geometric transforms (translation, rotation, etc.)
 Data reduction (cropping, clipping, etc.)
 Transcoding (MPEG2 ⇒ H.263, etc.)
 D/A and A/D conversion (print-scan, etc.)
 Multiple watermarking
 Collusion attack
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26. Multiple watermarking
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27. Characteristics of Digital Watermarks
 Unobtrusive: invisible enough not to degrade the data quality
and to prevent an attacker from finding and deleting it.
 Readily Detectable: the data owner or an independent control
authority should easily detect it.
 Unambiguous: retrieval of it should unambiguously identify
the data owner.
 Innumerable: it should be possible to generate a large number
of watermarks, all distinguishable.
 Robust: difficult to remove for an attacker, who would like to
destroy it in order to counterfeit the copyright of the data.
Moreover, removal of it should cause a considerable
degradation in the quality of the data.
 Visible watermarks should be visible enough to discourage
theft.
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28. Applications
 Embed information about the owner to prevent others
from claiming copyright
 For example, a compliant DVD player will not
playback or copy data that carry a “copy never”
watermark
 This is useful to monitor or trace back illegally
produced copies of the cover
 Used to avoid unauthorized duplication and
distribution.
 Digital watermark inserted to indicate the number of
copies permitted.
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29. Thank You