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TRANSPOSITION CIPHER

Introduction:
In cryptography, a transposition cipher is method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the cipher text constitutes a permutation of the plaintext. That is, the order of the units is changed. Mathematically a bijective function is used on the characters' positions to encrypt and an inverse function to decrypt.
In a columnar transposition, the message is written out in rows of a fixed length, and then read out again column by column, and the columns are chosen in some scrambled order. Both the width of the rows and the permutation of the columns are usually defined by a keyword. For example, the word ZEBRAS is of length 6 (so the rows are of length 6), and the permutation is defined by the alphabetical order of the letters in the keyword. In this case, the order would be "6 3 2 4 1 5".
In a regular columnar transposition cipher, any spare spaces are filled with nulls; in an irregular columnar transposition cipher, the spaces are left blank. Finally, the message is read off in columns, in the order specified by the keyword.




HOW TO CONDUCT THE EXPERIMENT:
Click on Presentation Layer on the Main Window and Then Select "TRANSPOSITION CIPHER" Module from the Modules displayed in the centre of the window.
TRANSPOSITION CIPHER Window will open up as shown in SNAPSHOT-1.

SNAPSHOT-1
TRANSMITTER:

1. Enter the "IP Address" of the computer to which you intend to send data.
2. Enter the Key for Encryption. The key value is between 5 digits each digit between 1 and 5. The key determines the column order for encryption.
3. Enter the Data that needs to be encrypted in the "TEXT" textbox.
4. Click on "ENCRYPT" button to encrypt the data.
The table displays the columnar Cipher Table as shown in SNAPSHOT-2.
The Encrypted Data is shown in the "ENCRYTED TEXT" textbox.

5. Click on the "SEND" button to send the encrypted Data to the destination IP.

SNAPSHOT-2


Use Loop back Address "127.0.0.1" to send the Data to the same computer.





RECEIVER:
In the Receiver Window, the Encrypted Data is displayed in the "ENCRYTED TEXT" text box as soon as the data is received as shown in SNAPSHOT-3.

SNAPSHOT-3

1. Enter the Key value same as entered on the server in the "KEY" textbox.
2. Click on "DECRYPT" button to decrypt the data. The Decrypted data is shown in the "TEXT" textbox on the receiver as shown in SNAPSHOT-4
And the Transposition Cipher Table is shown in the table at the bottom of the Receiver Window.


SNAPSHOT-4
Transmitter and Receiver Messages are Displayed in the "Message Window" on the extreme right.
Reset Button:
Click On "RESET BUTTON" to reset all the controls to initial values.
Click on "HELP BUTTON" to Open TRANSPOSITION CIPHER Manual.
Click on "EXIT BUTTON" To Close TRANSPOSITION CIPHER Window.

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