2. OUTLINES
o Introduction
o History
o Steganography V/S Cryptography
o Steps Involved In Steganography
o Stegnography In Various Media
o Digital Watermarking
o Watermarking V/S Steganography
o Steganalysis
o Advantage & Disadvantage
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3. Introduction
o Greek Words: STEGANOS – “Covered”
GRAPHIE – “Writing”
o Advance security is not maintained by the password protection
but it is gained by hiding the existence of the data, which can
only be done by Steganography
o Steganography is the art and science of writing hidden messages
in such a way that no one apart from the intended recipient
knows of the existence of the message
o This can be achieve by concealing the existence of information
within seemingly harmless carriers or cover
o Carrier: text, image, video, audio, etc.
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4. History
o Greeks used it writing message on some material
and later covering it with wax, tattooing messages
on bald head, later growing hair to cover it up.
o In World War II invisible inks were used to write
messages in between the lines of normal text
message.
o Currently, cryptography and steganography are
used to hide and send the secret data.
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5. Steganography V/S
Cryptography
o Cryptography hides the contents of a secret message
from a malicious people, whereas Steganography even
conceals the existence of the message.
o In cryptography, the structure of a message is
scrambled to make it meaningless and unintelligible
unless the decryption key is available.
o Steganography does not alter the structure of the secret
message, but hides it inside a cover-image so it cannot
be seen.
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9. Steganography In Text/Documents
It involves three types of coding:
o Line-Shift Coding : Here, text lines are vertically shifted to
encode the document uniquely.
o Word-Shift Coding : The code words are coded into document
by shifting the horizontal locations of words within text lines, while
maintaining a natural spacing appearance.
o Feature Coding : In feature coding, certain text features are
altered, or not altered, depending on the codeword.
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10. Hiding a Message inside Text
Partially effective
o randoM capitalosis is a rarE disEase ofTen
contrAcTed by careless inTernet users. tHis sad
illnEss causes the aFfected peRsON To randomly
capitalize letters in a bOdy oF texT. Please do not
confuse this disease witH a blatant
attEmpt aT steganogRAPhy.
Reveals: MEET AT THE FRONT OF THE TRAP
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11. Steganography In Images
o
Image Compression:
Image compression offers a solution to large image files. Two kinds of image
compression are lossless and lossy compression. Both methods save storage
space but have differing effects on any uncompressed hidden data in the image.
o
“Lossy”
JPEG(Joint Photographic Experts Group) format files, offers high
compression, but may not maintain the original image's integrity. Hence it is
called “lossy”.
“Lossless” compression maintains the original image data exactly, It is thus more
favored by steganographic techniques. Eg: (BMP ),(GIF) Formats.
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13. L.S.B Steganography
o Replacing least-significant-bits (LSBs) of digital data with
message bits.
110010
00
Embedding
Extracting
o Embedding random message bits in LSBs will not cause
any discernible difference from the cover-signals.
o Easy to implement, High payloads.
o 13
Simple, but susceptible to lossy compression and image
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manipulation.
14. L.S.B Uses
o Storing passwords and/or other confidential information
o Covert communication of sensitive data
o Speculated uses in terrorist activities
o Being widely used to hide and/or transfer illegal content
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15. WATERMARKING
o A watermark is a form, image or text that is impressed
onto paper, which provides evidence of its authenticity.
o A distinguishing mark impressed on paper during
manufacture; visible when paper is held up to the light.
o EXAMPLEThe presence of specific patterns in currency notes
which are visible only when the note is held to light is a
well known example for watermark.
Courtesy of Blue Spike, Inc.
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16. DIGITAL WATERMARKING
• Digital
watermarking is an extension
watermarking concept in the digital world.
of
• A digital watermark is a pattern of bits inserted into
a digital image, audio or video file that identifies the
file's copyright information (author, rights, etc.).
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17. STEGANOGRAPHY V/S
WATERMARKING
The
main goal of
steganography is to hide
a message m in some
audio or video (cover)
data d, to obtain new
data
d',
practically
indistinguishable from
d, by people, in such a
way
that
an
eavesdropper
cannot
detect the presence of m
in d'.
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The
main goal of
watermarking is to hide
a message m in some
audio or video (cover)
data d, to obtain new
data
d',
practically
indistinguishable from
d, by people, in such a
way
that
an
eavesdropper
cannot
remove or replace m in
d'.
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18. Importance of Digital
Watermarking
o As seen above in Fig, Alice creates an original image
and watermarks it before passing it to Bob. If Bob
claims the image and sells copies to other people Alice
can extract her watermark from the image proving her
copyright to it.
o The caveat here is that Alice will only be able to prove
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her copyright of the image if Bob hasn’t managed to
modify the image such that the watermark is damaged
enough to be undetectable or added his own watermark
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such that it is impossible to discover which watermark
20. Visible Watermarking
Visible watermark is a translucent overlaid into an
image and is visible to the viewer. Visible
watermarking is used to indicate ownership and for
copyright protection.
MAHESH Watermark
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Original Image
Watermarked Image2/25/2014
21. Invisible watermark
o Invisible watermark is embedded into the data in such a way that the
changes made to the pixel values are perceptually not noticed. Invisible
watermark is used as evidence of ownership and to detect
misappropriated images.
Original Image
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Watermarked Image
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23. PHASE CODING:
Phase coding relies on the fact that the phase components of sound
are not as perceptible to the human ear as noise is. Rather than
introducing perturbations, the technique encodes the message bits as
phase shifts in the phase spectrum of a digital signal, achieving an
inaudible encoding .
ECHO-HIDING:
In echo hiding, information is embedded in a sound file by
introducing an echo into the discrete signal. Like the spread spectrum
method, it too provides advantages in that it allows for a high data
transmission rate and provides superior robustness when compared to
the noise inducing methods.
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24. ADVANTAGE & DISADVANTAGE
ADVANTAGES :
Difficult to detect and Only receiver can detect
It can be done faster with large no. of softwares
Provides better security for sharing data in LAN, MAN & WAN
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.
If this technique is gone in the wrong hands like hackers can be very much dangerous for
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25. Detecting Steganography :
• The art of detecting Steganography is referred to as
Steganalysis.
• Steganalysis does not deal with trying to decrypt the
hidden information inside of a file, just discovering it.
• It is mainly done with comparing the encrypted file with
the original copy.
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