high capacity image steganography
TRANSCRIPT
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BY:
DEEPAK KUMAR CHAURASIA (10/CS/102)
SOURAV KARAN (10/CS/94)PAWAN KUMAR (10/CS/90)
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What is STEGANOGRAPHY ? Steganography is the art and science
to hide data in a cover that can be text,audio, image, video, etc.
ORIGIN : Greek words stegos
meaning cover and graf ia meaningwriting, defining it as covered
writing.
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History Greek historian Herodotus writes of a nobleman,
Histaeus, who needed to communicate with his son-
in-law in Greece. He shaved the head of one of his
most trusted slaves and tattooed the message onto
the slave's scalp. When the slave's hair grew backthe slave was dispatched with the hidden message.
In the Second World War the Microdot technique was
developed by the Germans. Information, especially
photographs, was reduced in size until it was the
size of a typed period. Extremely difficult to detect, a
normal cover message was sent over an insecure
channel with one of the periods on the paper
containing hidden information.
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Steganography vs. Cryptography
Cryptography hides the contents of a secret
message from a malicious people, whereas
steganography even conceals the existence
of the message. In cryptography, the structure of a message
is scrambled to make it meaningless and
unintelligible unless the decryption key is
available, Whereas in 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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Categories of Steganography
In Image Steganography the information ishidden exclusively in images.
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IMAGE STEGANOGRAPHYHiding Data in Images
Even though audio and video files offer a
much higher capacity to hide information,
digital images are more easily disguised
and can be exchanged on a much lower
bandwidth.
Image steganography techniques can be
broadly classified into two categories-
spatial domain techniques and transform
domain techniques.
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Spatial Domain techniqueSpatial domain technique directly modify the
image intensity values to embed the secret
information. The most common spatial domaintechnique is the least significant bit (LSB)
manipulation technique, where the LSB of the
each intensity value is replaced with one bit of
the secret data. Other spatial domaintechnique include contrast adjustment, noise
insertion etc.
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Transform Domain technique
Transform domain technique modify the
transform coefficients of the image. The
transform coefficients are obtained by applying
transforms, such as the Fourier transform,Discrete Cosine transform (DCT) or the Wavelet
transform, to the image. Since most images are
compressed by manipulating transform
domain coefficients, the transform domain
techniques add a fair amount of robustness
against the destruction of the secret data due
to lossy image compression.
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Scenario
It was used in 9/11 WTC Attack in 2001. For Communication, Terrorists used
Pictures Mail of few celebrities.
For about 6-7 months, no security
professional have any idea what thesepictures mail are.
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Applications ofImage Steganography
Covert military communications.
Covert police communications.
Digital Rights Management protecting intellectual
property such as images, music, electronic books,etc.
Embedding textual data in medical images would
better ensure that the picture belongs to a particular
patient.
There are some nefarious applications also. Such as-
money laundering, drug running, child pornography,
spying (good or bad depending upon which side
youre on!), terrorism etc.
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ModulesThe Steganography consists of mainly four
modules Encryption, Hide message, Retrieve
message and Decryption.
Encryption and Hide message form the
modules at the sender side.
Retrieve message and Decryption form the
modules at the Receiver side.
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Encryption
Secret key can be used for encryption
of the message to be hidden. It
provides security by converting it into acipher text, which will be difficult for
hackers to decrypt. Moreover if the
message is password protected, then
while retrieving message, the retrieverhas to enter the correct password for
viewing the message.
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Hide Message
Hiding message is the most important module of
steganography. It involves embedding the message
into the cover text. Each pixel typically has three
numbers associated with it, one each for red, green,and blue intensities, and these values often range
from 0-255.In order to hide the message, data is first
converted into byte format and stored in a byte array.
The message is then encrypted and then embed each
bits into the LSB position of each pixel position. The
least significant (right most) bit of each 8-bit byte has
been co-opted to hide a text message.
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Retrieve Message
It involves retrieving the embed
message from the file (independent of
the file format). Once the message has
been retrieved it has to be converted
into original message or file. This can
be done by reading the embedded data
from the master file. The read data willbe in the bytes format. This message
has to be converted into the suitable
output file format.
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Decryption
Decryption involves converting the
cipher text into decrypted format.
Secret key can be used for decryptionof the message that is hidden. It
provides security by converting the
cipher text, into the original datamessage or file.
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Classical technique for Image Steganography
The simplest steganographic technique that
embed the bits of the message directly into least
significant bit plane of the cover- image in adeterministic sequence.
The least significant bit (the 8th bit) of some or all
of the bytes inside an image is changed to a bit of
the secret message. When using a 24-bit image, abit of each of the red, green and blue color
components can be used, since they are each
represented by a byte. In other words, one can
store 3 bits in each pixel.
Least s ign i f icant b i t (LSB)
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An 800 600 pixel image, can thus store a total
amount of 1,440,000 bits or 180,000 bytes ofembedded data.
For example, a grid for 3 pixels of a 24-bit image can
be as follows:
(00101101 00011100 11011100)
(10100110 11000100 00001100)(11010010 10101101 01100011)
When the number 200, which binary representation is
11001000, is embedded into the least significant bits ofthis part of the image, the resulting grid is as follows:
(00101101 00011101 11011100)
(10100110 11000101 00001100)
(11010010 10101100 01100011)
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Disadvantage ofLSB technique For the hiding capacity, the size of information to
be hidden relatively depends to the size of the
cover- image. The message size must be smaller
than the image. A large capacity allows the use ofthe smallercover- imagefor the message of fixed
size, and thus decreases the bandwidth required
to transmit the stego-image.
Another weakness is an attacker can easily
destruct the message by removing the entire LSB
plane with very little change in the perceptual
quality of the modified stego-image.
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Technique for
HIGH CAPACITY IMAGE
STEGANOGRAPHY-------------------------------------------------------
Wavelet Transform Technique-------------------------------------------------------
As compared to transform domain data hiding methods,this scheme can provide a larger capacity for data hiding
without sacrificing the cover image quality. This is achieved
through retaining integrity of the wavelet coefficients at
high capacity embedding.
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Wavelet transform technique
Wavelets transform (WT) converts spatial domain
information to the frequency domain information. Wavelets
are used in the image steganographic model because the
wavelet transform clearly partitions the high-frequency and
low-frequency information on a pixel by pixel basis. Thediscrete wavelet transform (DWT) method is favored over
the discrete cosine transform (DCT) method, owing to the
resolution that the WT provides to the image at various
levels. Wavelets are mathematical functions that divide
data into frequency components, which makes them ideal
for image compression. In contrast with the JPEG format,
they are far better at approximating data with sharp
discontinuities.
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Evaluation of different techniquesAll steganographic algorithms have to comply witha few basic requirements. The most important
requirement is that a steganographic algorithm has
to be imperceptible. There are several parameters tomeasure the performance of the steganographic
system.
These parameters are as follows:
Invisibility
Payload capacity Robustness against statistical attacks
Robustness against image manipulation
Independent of file format
Unsuspicious files
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THANKYOU ALL