High Capacity Image Steganography

7/30/2019 High Capacity Image Steganography

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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

High Capacity Image Steganography

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