Transposition Techniques PDF

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This notes leads you to gain knowledge of Transposition Techniques used for Encryption Algorithm with some examples....

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TRANSPOSITION TECHNIQUES ● Transposition technique is a cryptographic technique that converts the plain text to cipher text by performing permutations on the plain text i.e change the position of each character of plain text for each round. eg: ABC ---> ABC, ACB,BCA,BAC,CBA,CAB

● There are two types of Transposition techniques: 1. Rail Fence Cipher 2. Row Transposition

RAIL FENCE CIPHER ● In a transposition cipher, the order of the alphabets is rearranged to obtain the cipher-text. ● In the rail fence cipher, the plain-text is written downwards and diagonally on successive rails of an imaginary fence. ● When we reach the bottom rail, we traverse upwards moving diagonally, after reaching the top rail, the direction is changed again. Thus the alphabets of the message are written in a zig-zag manner. After each alphabet has been written, the individual rows are combined to obtain the cipher-text. EXAMPLE -1:: Plaintext : BITSEDU B

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Cipher Text: BTEUISD EXAMPLE-2 :: Original Message: HELLO WORLD Key: 3

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Encrypted Message : HOREL OLLWD

EXAMPLE - 3 :: Plain Text: T H I S I S A S E C R E T M E S S A G E key=3

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Encrypted Messae: T I E T S H S S S C E M S A E I A R E G

EXAMPLE- 4 :: Plain Text: M E E T M E I N T H E C L A S S Key=2

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Encrypted Message: M E M I T E L S E T E N H C A S

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ROW TRANSPOSITION TECHNIQUE ● A more complex scheme is to write the message in a rectangle, row by row, and read the message off, column by column, but permute the order of the columns. The order of the columns then becomes the key to the algorithm.

Encryption : Key CRYPTO ( unique digits from 0 to 9)

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EXAMPLE-1 : key 4 3 1 2 5 6 7 Plain Text : attackpostponeduntiltwoam 4

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Cipher Text: (Writting in order) 1 2 3 ttna aptm tsuo

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Cipher Text: ttnaaptmtsuoaodwcoixknlypetz

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❏ Double Transposition:

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Cipher Text: nscyauopttwltmdnaoiepaxttokz...