Transposition Techniques 5n553z

TRANSPOSITION TE CHNIQUES ROLL NO.

NAME

16

HETANSH BHARAD

34

SUKANTA PATRA

INDEX PAGE

TOPICS

1.

RAIL FENCE TECHNIQUE

2.

SIMPLE COLUMNAR

3.

STEGANOGRAPHY

PAGE NO.

STEGANOGRAP HY

Steganography What is Steganography?   

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def’n:        the art and science of  hiding information by      embedding it in some  cryptography ­ render message unintelligible other data. steganography ­ conceal the existence of the message

STEGANOGRAPHY VS CRYPTOGRAPHY

Steganography can be viewed as akin to cryptography. Both have been used throughout recorded history as means to protect information. At times these two technologies seem to converge while the objectives of the two differ. Cryptographic techniques "scramble" messages so if intercepted, the messages cannot be understood. Steganography, an essence, "camouflages" a message to hide its existence and make it seem "invisible" thus concealing the fact that a message is being sent altogether. An encrypted message may draw suspicion while an invisible message will not. Steganography cannot be detected. Therefore, it is used when encryption is not permitted. Or, more commonly, steganography is used to supplement encryption. An encrypted file may still hide information

EVOLUTION OF STEGANOGRAPHY  INVISIBLE INK : An innocent letter may contain a very different message written between the lines with invisible ink. Common sources for invisible inks are milk, vinegar, fruit juices and urine. All of these darken when heated. Later on, more sophisticated inks were developed which react to various chemicals.  MICRODOTS: The Germans developed microdot technology. Microdots are photographs the size of a printed period having the clarity of standard-sized typewritten pages. The first microdots were discovered masquerading as a period on a typed envelope carried by a German agent in 1941. The message was not hidden, nor encrypted. It was just so small as to not draw attention to itself (for a while). Besides being so small, microdots

Steganography info          

info

         ­file         embed

        extract

The cover provides a host for transporting the hidden info.

AN EXAMPLE

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Fishing freshwater bends and saltwater coasts rewards anyone feeling stressed. Resourceful anglers usually find masterful leapers fun and a dmit swordfish rank overwhelming anyday. “Send lawyers guns and money”

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Most communication channels like telephone lines and radio broadcas ts transmit signals which are always accompanied by some kind of noi se. This noise can be replaced by a secret signal that has been transfor med into a form that is indistinguishable from noise without knowledg e of a secret key and this way, the secret signal can be transmitted un detectable.

DISSECTING STEGANOGR APHY Steganography is a term used for hiding messages within an image. Any color pixel is made of a combination of red –green-blue mode(RGB) wherein each RGB component consist of 8 bits. If letters in ASCII are to be represented within the color pixels, the rightmost digit, called the least significant bit (LSB), can be altered. Any variation in the value of this bit leads to very minimal variation in color. If we have to hide the word ‘digit’ in the image, we take the LSB of every color and hide each bit of the word in its RGB combination. To insert the letter ‘D’ we modify three color pixels with three bits in each color pixel, we utilize

DISSECTING STEGANOGRAPHY……..

00000000 11111111 CHARACTER CODE

10101010

01010100 01010100 10101010 D-01000100 01010100 01010100 G-01100111 I-01101001 T-01110100

ASCII

I-01101001

MSB

AMOUNT OF DATA STORED INSIDE A PICTURE

DISSECTING STEGANOGRAPHY Suppose we have a 24-bit image 1024 x 768 (this is a common resolution for satellite images, electronic astral photographs and other high resolution graphics). This may produce a file over 2 megabytes in size (1024x768x24/8 = 2,359,296 bits). All color variations are derived from three primary colors, Red, Green and Blue. Each primary color is represented by 1 byte (8 bits). 24-bit images use 3 bytes per pixel. If information is stored in the least significant bit (LSB) of each byte, 3 bits can be a stored in each pixel. The "container" image will look identical to the human eye, even if viewing the picture side by side with the original.

STEPS FOR HIDING AN IM AGE USING STEGANOGRA PHY  Start s-tool and window explorer using the later as drag and drop interface the software.  Drag and drop the image to be used as the carrier file from the explorer onto the actions window in s-tool.  Drag and drop the data file on the carrier file.  Give phrase and encryption prompted. these to receiver too.

algorithm

when

 The hidden file is ready. Receiver has to click on the “reveal” button to extract the data.

SOME OUTSTANDING FAC TS 1.     steganos security suite 4 uses powerful 128-bit encryption. It would take 1 billion powerful computers million of years to try every combination to gain access to your personal information. this software uses steganography along with encryption to completely secure your data.   2.     Blindside is an application of steganography that allows you to conceal a single file or set of files within a standard computer image. The new image looks identical to the original, but can contain up to 50k of data. The hidden files can also be encrypted to prevent unauthorized access.   3.     Mp3stego hides information in mp3 files during the compression process. The data is first compressed, encrypted and then hidden in the mp3 bit stream. Although mp3stego was written with steganographic applications in mind, it can also be used as a

ADVANTAGES OF STEGA NOGRAPHY

Ø     It can be used for safeguarding data, such as in the field of media where copywriting ensures authenticity. Ø     It can be used by intelligence agencies for sending their secret data.

DISADVANTAGE OF STEGANOGRA PHY

Many a terrorist and anti humanist activities have been carried out cloaked under this technique. The most famous and recent attack recorded was the 9/11 attack on the Twin towers.

RAIL FENCE TRANSPOSITION

RAIL FENCE TRANSPOSITION 1. The rail fence cipher is an easy to apply trans position cipher that jumbles up the order of t he letters of a message in a quick convenient way. It also has the security of a key to make i t a little bit harder to break 2. The Rail Fence cipher works by writing your m essage on alternate lines across the page, and then reading off each line in turn. For exampl e, the plaintext "defend the east wall" is writte n as shown below, with all spaces removed.

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The simplest Rail Fence Cipher, where each letter is written i n a zigzag pattern across the page. The cipher-text is then read off by writing the top row first, f ollowed by the bottom row, to get "DFNTEATALEEDHESWL".

ENCRYPTION 

To encrypt a message using the Rail Fence Cipher, you hav e to write your message in zigzag lines across the page, an d then read off each row. Firstly, you need to have a key, which for this cipher is the number of rows you are going to have. You then start writing the letters of the plaintext diagonally down to the right until you reach the number o f rows specified by the key. You then bounce back up diag onally until you hit the first row again. This continues until the end of the plaintext.

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For the plaintext we used above, "defend the east wall", with a key of 3, we get the encryption process shown below.

The Rail Fence Cipher with a key of 3. Notice the nulls added a t the end of the message to make it the right length.

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Note that at the end of the message we have inserte d two "X"s. These are called nulls, and act as placeho lders. We do this to make the message fit neatly in to the grid (so that there are the same number of letter s on the top row, as on the bottom row. Although no t necessary, it makes the decryption process a lot ea sier if the message has this layout. The cipher-text is read off row by row to get "DNETLE EDHESWLXFTAAX".

DECRYPTION 

The decryption process for the Rail Fence Cipher involves r econstructing the diagonal grid used to encrypt the messa ge. We start writing the message, but leaving a dash in pla ce of the spaces yet to be occupied. Gradually, you can re place all the dashes with the corresponding letters, and re ad off the plaintext from the table.

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We start by making a grid with as many rows as the key is, an d as many columns as the length of the cipher-text. We then place the first letter in the top left square, and dashes diagon ally downwards where the letters will be. When we get back t o the top row, we place the next letter in the cipher-text. Con tinue like this across the row, and start the next row when yo u reach the end. For example, if you receive the cipher-text "TEKOOHRACIRMN REATANFTETYTGHH", encrypted with a key of 4, you start by p lacing the "T" in the first square. You then dash the diagonal down spaces until you get back to the top row, and place the "E" here. Continuing to fill the top row you get the pattern b elow.

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The first row of the decryption process for the Rail Fence Cip her. We have a table with 4 rows because the key is 4, and 28 columns as the cipher-text has length 28.

Continuing this row-by-row, we get the successive stages

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The second stage in the decryption process.

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The third stage in the decryption process.

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The fourth and final stage in the decryption process.

From this we can now read the plaintext off following the diago nals to get "they are attacking from the north".

Example:Entering data and Encrypting it.

Decrypting the data.

SIMPLE COLUM NAR TRANSPOS ITION

Columnar Transposition 

A Columnar Transposition is a more complex sch eme would be to write the message in rectangula r form, row by row, and then to read the charact ers column by column.

The number of columns is the key information.

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To encipher : Plaintext is written horizontally in k columns, and is then transcribed vertically column- by-column.

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To decipher : Suppose that the length of the ciphertext is n and the key is k . Then the letters will fill n DIV k full row s, and there will be one partial row at the end with n MO D k letters. Transcribing row-by-row will then yield the plaintext.

Example: Encrypt NOTHING IN THE WORLD IS MORE DANG EROUS THAN SINCERE IGNORA NCE AND CONSCIENTIOUS STUPI DITY with a key of k = 9 column s.

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Solution: We write the plaintext horizontally in 9 columns as fo llows:

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The cipher text is therefore: NTS ES NDTIO HMRIO CIDTE OONRO OIHWR UCANU TIOES ENSSY NRDTR CCSGL AHEEI TIDNA IAEUN IGNGN N P.

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Example: Suppose the ciphertext is: GPSDO AILTI VRVAA WETEC NITHM EDLHE TALEA ONME. If it is known that the key is k = 7, find the plaintext. Solution: There are 39 letters in the ciphertext which means that there are 39 DIV 7 = 5 full rows and one partial row with 39 MOD 7 = 4 letters. g p s d o a

i l t i v r

v a a w e t

e c n i t h

m e d l h

e t a l e

a o n m e

×

×

×

Plaintext: give me a place to stand and i will move the earth

*

Keyword Columnar Trans position The order of transcription of the columns is determine d by the alphabetical order of letters in the keyword. If there are repeated letters in the keyword, the columns c orresponding to those letter s are transcribed in order left-to-right.

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Example: Encrypt THE QU ICK BROWN FOX JUMP ED OVER THE LAZY D OG if the keyword is CORN EIL.

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C

O

R

N

E

I

L

1

6

7

5

2

3

4

T

H

E

Q

U

I

C

K

B

R

O

W

N

F

O

X

J

U

M

P

E

D

O

V

E

R

T

H

E

L

A

Z

Y

D

O

G

X

X

X

X

• Ciphertext: TKODE YINPT DCFEH ZHBXO LERJV A

X

GUWMR OQOUE

X

Cryptanalysis of a Columnar Transp osition For a simple columnar transposition, cryptanalysis is relatively direct. Attempt to decipher with various numbers of columns until intelligible plaintext appears. Example: Cryptanalysis the following: LAEST HWAOB ANHED MIEAO TLWOA ESUEN CAETU LDIVT IAUSE ILADE TMOCI OREHP SCSTC DROTS EOHVN Note that there are n = 75 letters. Solution: If k = 2 we have L A E

V T I SA TU .. ..

If k = 3 we have L E T A M and so the Splaintext is LETASMEUOSECTNI .... E U O S E C T N I

I

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f

k =

4

w

And so the plaintext is LOVEATTHELIPSWASTOUC....

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If we continue the decry ption, we find ... ... ... ..

Love at the lips was touch As sweet as I could bear; And once that seemed too much; I lived on air -Robert Frost (from To Earthward )

H W A O B A N H E D M I E A

A S E E S I U L E A N D C E A T E M T O

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S T C D R O T S E

REFERENCES • WWW.STUDYMAFIA.ORG • IMAGES FROM 'SPY VS SPY' FROM MAD MAGAZINE ANTONIO PROHIAS • WWW.WIKIPEDIA.ORG • https://www.google.co.in/url?sa=i&rct=j&q=&esrc=s& source=images&cd=&cad=rja&uact=8&ved=0ahUKEwir -5inzaDOAhXLPI8KHem6DMkQjRwIBw&url=http%3A%2 F%2Fwww.topinfopost.com%2F2014%2F02%2F26%2F7 5-top-professors-and-leading-scientists-claim-911-was-insi de-job&psig=AFQjCNFuJrqAFKM3gCESzjOIQS-iJxOeIA& ust=1470153737369578

REFERENCES • FROM TO EARTHWARD- ROBERT FROST • http://stat.math.uregina.ca/~kozdron/Teaching/Cor nell/135Summer06/Handouts/transposition.pdf

THANK YOU!!!