This document provides an overview of steganography and watermarking techniques for hiding information in digital media. It defines steganography as "covered writing" involving hiding secret messages within other digital files like images, audio, or video. Common steganography methods embed data in the least significant bits of pixels or audio samples. Watermarking differs in embedding identifying marks that are robust to modifications and aim to protect copyrights. The document outlines various media and techniques for each, applications, advantages and limitations of both steganography and watermarking.

1. steganography
&
watermarking
by Sudip Nandi

2. OVERVIEW
Information hidding
Steganography Defined
Block diagram
Steganography in various media
Steganalysis
Application
Advantages and Disadvantages
Watermarking

3. INTRODUCTION
Information Hiding Techniques
Information Hiding
Steganography Watermarking
3

4. Information Hiding
Information Hiding : Communication of
information by embedding in original data and
retrieving it from other digital data.
Depending on application we may need process to
be imperceptible, robust, secure. Etc.

5. Where can we hide?
Media
 Video
 Audio
 Still Images
 Documents
Software
Etc.
We focus on data hiding in media.
We mainly use images but techniques and concepts
can be suitably generalized to other media.

6. Why Hide?
Because you don’t want any one to even know about its
existence.
Covert communication – Steganography
Because you want to protect it from malicious use.
copy protection and deterrence - Digital Watermarks

7. STEGANOGRAPHY

8. STEGANOGRAPHY DEFINED
The word steganography comes from the
Greek ‘steganos’ , meaning covered or secret,
and ‘graphy’ , meaning writing or drawing.
Therefore, steganography literally means –
“covered writing”.

10. STEGANOGRAPHY UNDER VaRIOUS MEDIA
 Steganography in “TEXT”
 Steganography in “IMAGES”
 Steganography in “AUDIO”

11. STEGANOGRAPHY IN TEXT
It involves three types of coding:
Line-Shift Coding : Here, text lines are vertically shifted to
encode the document uniquely.
 Word-Shift Coding : The codewords are coded into a
document by shifting the horizontal locations of words
within text lines, while maintaining a natural spacing
appearance.

12. STEGANOGRAPHY IN IMAGE
Digital images are made up of pixels.
The arrangement of pixels make up the
image.
Each pixel can have 8-bit(Gray image)
and 24-bit(Color image) binary number.
The larger the image size, the more
information you can hide. However, larger
images may require compression to avoid
detection

13. GRAYSCALE PALETTE

14. NEBULA PALETTE

15. IMAGE-BASED TECHNIQUES
Least Significant Bit Insertion :
Replaces least significant bits with the message to be encoded
A sample raster data for 3 pixels (9 bytes)
00100111 11101001 11001000
00100111 11001000 11101001
11001000 00100111 11101011
00100110 11101001 11001000
00100110 11001000 11101000
11001000 00100111 11101011
Inserting
the binary
value for
A
(01000001)
changes
4 bits

16. STEGANOGRAPHY IN AUDIO
Audio Environments
Digital representation
In audio steganography, secret message is embedded into
digitized audio signal which result slight altering of binary
sequence of the corresponding audio file. There are several
methods are available for audio steganography. We are going to
have a brief introduction on some of them.

17. STEGANOGRAPHY IN AUDIO
Methods of Audio Data Hiding
LSB techniques:
Phase coding :

18. STEGANALYSIS
Here 2 methods of Steganalysis are looked into :
 detecting messages or their transmission
 disabling embedded information

19. RELATION BETWEEN STEGANOGRAPHY
AND STEGANALYSIS

20. APPLICATION OF STEGANOGRAPHY
Confidential communication and secret data storing
Protection of data alteration
Media database system

21. • ADVANTAGES :
 Difficult to detect and Only receiver can detect.
 It can be done faster with large no. of softwares.
DISADVANTAGES :
 The confidentiality of information is maintained by the algorithms, and
if the algorithms are known then this technique is of no use.
 Password leakage may occur and it leads to the unauthorized access
of data.
ADVANTAGE AND DISADVANTAGE OF STEGANOGRAPHY

22. STEGANOGRAPHY VS WATERMARKING
Watermarking is a process in which the information which
verifies the owner is embedded into the digital image or signal.
These signals could be either videos or pictures or audios;
steganography is changing the image in a way that only the
sender and the intended recipient are able to detect the
message sent through it.
 Watermarking is of two types; visible watermarking and
invisible watermarking.
 Steganography is typically invisible.

23.  The ease in use and abundant availability of steganography tools
has law enforcement concerned in trafficking of illicit material via web
page images, audio, and other transmissions over the Internet.
 This seminar provides an overview of steganalysis and introduced
some characteristics of steganographic software that point signs of
information hiding.
Formerly, just an interest of the military, steganography is now
gaining popularity among the masses.
CONCLUSION

24. Digital Watermarks

25. What is a Watermark?
A watermark is a “secret message” that is embedded
into a “cover message”.
Usually, only the knowledge of a secret key allows us
to extract the watermark.
Visible Watermarking Invisible Watermarking

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History
• The Italians where the 1st to use watermarks in the
manufacture of paper in the 1270's.
• A watermark was used in banknote production by the
Bank of England in 1697.
It is a good security feature because the watermark
cannot be photocopied or scanned effectively.

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Why Watermark? Motivation
 Copyright protection of multimedia data
Copyright owners want to be compensated every time their work
is used.
 The need to limit the number of copies created whereas
the watermarks are modified by the hardware and at some
point would not create any more copies (i.e. DVD) - the
reading device must be able to modify the watermark
 Content protection – content stamped with a visible
watermark that is very difficult to remove so that it can be
publicly and freely distributed

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Watermarks Classification
1. Paper Watermark: Intended to be somewhat visible.
2. Digital Watermark: A digital signal or pattern
imposed on a digital document ( text, graphics,
multimedia presentations , …).

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Paper Watermark
The technique of impressing into the paper a
form of image or text.
“Cannot be photocopied or scanned effectively”
Purpose: To make forgery more difficult to record the
manufacturer’s trademark, Copyright protection, logos,
etc …
Used in :
Currency, Banknotes , Passports, …

30. Paper watermark
Example

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Digital Watermarking Types
 Visible and Invisible:
 Visible such as a company logo stamped on an image or
Video.
 Invisible intended to be imperceptible to the human eye or
inaudible. the watermark can only be determined through
watermark extraction or detection by computers.
Visible Watermarking Invisible Watermarking

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Watermarking Process
• Two major steps:
– Location Selection : Where to embed watermark
– Processing : How to modify original data to embed
watermark

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Watermarking Embedding & Extraction
Cover Image Cover + WM
Embedding F : Watermarked Image = Function (Cover, Watermark, Key)
Extraction F : Watermark = Function (Watermarked Image, Key(
Cover + WM

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Watermarking Techniques
• Text – Varying spaces after punctuation, spaces in
between lines of text, spaces at the end of sentences, etc.
• Audio – Low bit coding, random.
• Images / Video – Least-significant bit, random

35. It is used for copyright protection.
It is used for source tracing.
Annotation of photographs.
APPLICATION OF WATERMARKING

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Limitations / Conclusions
• Rapidly growing field of digitized images, video and audio has
urged for the need of protection.
• Watermarking is a key process in the protection of copyright
ownership of electronic data (image, videos, audio, ...).
• Digital watermarking does not prevent copying or distribution.
• Digital watermarking alone is not a complete solution for
access/copy control or copyright protection.
• Digital watermarks cannot survive every possible attack.

37. REFERENCES
[4] L. Boney, A. Tewfik, and K. Hamdy, “Digital watermarks for
audio signals,” in IEEE Proc. Multimedia, 1996, pp. 473-480.
1)Petitcol Fabien A.P., “Information Hiding: Techniques for
Steganography and Digital
Watermarking.”, 2000.
2) StegoArchive, “Steganography Information, Software and News to
enhance your Privacy”,
2001, URL: www.StegoArchive.com
3) Petitcolas, Fabien A.P., “The Information Hiding Homepage: Digital
Watermarking and
Steganography”,
URL: http://www.cl.cam.ac.uk/~fapp2/steganography/

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