stegonagraphy

8/7/2019 STEGonaGraphy

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STEGANOGRAPHY


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What is it ?

According to Wikipedia :Steganographyis the art and science of writing hidden

messages in such a way that no

one apart from the sender and intended recipient even realizes there is a

hidden message.

The word comes from Greek steganos or covered andgraphie or writing meaning

covered or hidden writing.

Two examples of how it appeared:

1.Demaratus sent a warning about a forthcoming attack to Greece by

writing it on a wooden panel and covering it in wax.

2.Another ancient example is that ofHistiaeus encouragedAristagoras of

Miletus to revolt against Persian king. He shaved the head of his most

trusted slave and tattooed a message on it. After his hair had grown the

message was hidden.


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Real World Cases

Backbone Securityannounces the release of a new and improved

version of their Steganography AnalyzerReal-time Scanner,

StegAlyzerRTS V3.0 developed in Backbones Steganography Analysis

and Research Center (SARC), the only commercially available real-timeSteganographydetection system in the world. It uses digital

Steganography, such that a file can

be embedded within, or appended to, another file in such a way

that it cannot be seen or heardand conceals the very existence of the

information.

It is available for $14,995.00 for their business

partners worldwide.


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Real World Cases

Steganography is being used as a very powerful technique, even to CriminalOrganizations :

USA reported that bin Laden and others "are hiding maps and

photographs ofterrorist targets and posting instructions for terrorist activities on

sports chat rooms,pornographic bulletin boards and other websites, U.S. and foreign

officials say.

Hello Kitty images were used by Colombian Drug lordJuan Carlos RamirezAbadia to hide messages to his minions as Steganographyvector. Abadia apparently

picked Hello Kitty ashis courier because his wife was a big fan of the Japanese icon --

she had even decorated one of her rooms in a Brazilian house with Hello Kitty-themed

chairs, watches and wallpaper

The Hello Kitty Image

which was used as the

Stego Image


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The Modern Framework(The Prisoners Problem)

Here Alice and Bob are two Inmates who wish to communicate and Wendy

is the Warden and examines all the message passed between them.

Secret

Message

Secret

Message

Secret Key

Message

Retrieval

Algorithm

Suppress

Message

Stego

Message

Embedding

Algorithm

Cover

Message

Secret Key

Is Stego

msg?

ALICE WENDY BOB


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The Modern Framework(The Prisoners Problem)

Here Alice and Bob are two Inmates who wish to communicate and Wendy

is the Warden and examines all the message passed between them.

Now the warden(i.e. Wendy) can examine all messages :

Passive :

Examines all messages between Alice and Bob. Does not change any message.

For Alice and Bob to communicate Stego Objectshould be

Indistinguishable from cover object.

Active :

Deliberately alters message to thwart any hiddencommunication even if no secret message is suspected.

Steganographyagainst Active Warden is difficult.

Robust media watermark provides a potential way for

Steganographyin presence ofActive Warden.


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GeneralSteganography

Robustness

UndetectibilityCapacity

GoodSteganography

Robustness

Invisibility

Undetectibility

Signal to NoiseRatio

Capacity

TamperResistance

Most simple properties of

general Steganography

All key properties for

Good Steganography

Characteristics Of Strong Steganography


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Steganalysis In Practice

Techniques decided for a specific Steganography algorithm :

Good detection accuracy for the specific technique.Useless for a new technique.

Universal Steganalysis Techniques :

Less accurate in detection.

Usable on new embedding techniques.

We are using a specific Steganographic algorithm


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Embedding Technique

The Summarized Algorithm is as follows :

1. Select a seed pixel and take as input its matrix form.

2.S

elect the neighbouring pixels.

3. Find the absolute rounded DCT of the intensity of the neighbouring

pixels and find out and store the remainder after dividing it by 16.

Let the remainder be R .

4. Subtract R from the intensity and hence the resultant is divisible by

16.

Cont


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5. Now add different values to the resultant intensity according to the different

4 bit binary message to be embedded according to the table givrn below :-

MSG VALUETO BEADDED

0000 00001 1

0010 2

0011 3

0100 4

0101 5

0110 6

0111 71000 8

1001 9

1010 10

1011 11

1100 12

1101 131110 14

1111 15

6. The modified intensity is replaced in the original image matrix.

7. At the end we get the stego matrix embedded with the message.


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The summarized Algorithm is as follows :

1. Select a seed pixel and take as input its matrix form.

2. Select the neighbouring pixels.

3. Find the absolute rounded DCT of the intensity of the

neighbouring pixels and find out and store the remainder after

dividing it by 16. Let the remainder be R .

4. Now R represents the Decimal Value of the embedded message .

When converted to 4-bit binary format we get out resultant

message at the receivers end.

Extracting Technique


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Example ,,,,,,,,,,,,, incomplete ,,,,

:P

:D :D :D :D


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Questions . ???


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With Regards..!!!

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