Information And Data Security Steganography and Watermarking seminar Mustansiriya University Department of Education Computer Science

1. Steganography
and Watermarking
Lecture Slides
by
Israa

2. INTRODUCTION
Information Hiding Techniques
Information Hiding
Steganography Watermarking
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3. 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.

4. Where can we hide?
Media
 Video
 Audio
 Images
 Documents

5. 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

6. STEGANOGRAPHY
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”.

7. Steganography
 hides existence of message.
 Only sender and intended recipient know
there is a hidden message .
 It allows the people to communicate secretly.
 has drawbacks
 high overhead to hide relatively few
information bits
 Is a branch of information hiding.
 an alternative to encryption

8. Steganography & Cryptography
 Steganography and Cryptography are closely
related
 The difference is in their goals...
– Cryptography: although encypted and unreadable,
the existence of data is not hidden
– Steganography: no knowledge of the existence of
the data
 Steganography and Cryptography can be used
together to produce better protection

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

11. STEGANOGRAPHY IN TEXT
It involves two 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
 The most popular medium!
Least-significant bit (LSB) modifications

13. STEGANOGRAPHY IN AUDIO
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.
Methods of Audio Data Hiding
 LSB techniques
 Phase coding

14. STEGANALYSIS
Here methods of Steganalysis are looked into :
 Detecting and decoding the hidden data within a
given medium .
 disabling embedded information
 Even if secret content is not revealed, modifying the
cover medium changes the medium’s statistical
properties
 Distributed Dictionary Attack

15. RELATION BETWEEN STEGANOGRAPHY
AND STEGANALYSIS

16. APPLICATION OF STEGANOGRAPHY
 Confidential communication and secret data storing
 to have secure secret communications where cryptographic
encryption methods are not available, or strong
cryptography is impossible.
 Protection of data alteration
 Media database system
 In some cases, for example in military applications, even
the knowledge that two parties communicate can be of large
importance

17. ADVANTAGES :
 Difficult to detect and Only receiver can detect.
 It can be done faster with large no. of software.
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.
 high overhead to hide relatively few information bits
Advantages and Disadvantages Of Steganography

18.  Used primarily for identification and verify the
authentication .
 Embedding a unique piece of information within a
medium (typically an image) without noticeably
altering the medium
 Almost impossible to remove without seriously
degrading an image
 Usually, only the knowledge of a secret key allows
us to extract the watermark.
Watermarking
 A watermark is a “secret message” that is embedded
into a “cover message”.

19. 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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20. Why Watermark? Motivation
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 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

21. 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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22. 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, …
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23. Paper watermark
Example

24. Digital Watermarking Types
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 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

25. Watermarking Process
• Two major steps:
– Location Selection : Where to embed watermark
– Processing : How to modify original data to embed
watermark
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26. Watermarking Embedding & Extraction
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Cover Image Cover + WM
Embedding F : Watermarked Image = Function (Cover, Watermark, Key)
Extraction F : Watermark = Function (Watermarked Image, Key(
Cover + WM

27. 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
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28. STEGANOGRAPHY VS WATERMARKING
 The key difference is their goals...
– Steganography: hiding information
– Watermarking: extending the file with extra information
 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 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;

29. STEGANOGRAPHY VS WATERMARKING
 Steganography is typically invisible. Steganographic
information must never be apparent to a viewer unaware of its
presence.
 Watermarking is of two types; visible watermarking and
invisible watermarking.
 Digital watermarking hides data in a file, and the act of
hiding data makes it a form or steganography

30. 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.
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Thank you