Question

In: Computer Science

The Vigenère Cipher is an encryption algorithm that combines the use of a keyword with the...

The Vigenère Cipher is an encryption algorithm that combines the use of a keyword with the message to be encrypted. A tableau is provided that shows an encrypted character for each combination of characters in the message and the keyword.

Using the Vigenère Tableau encryption scheme with a keyword of KEYWORD, encrypt the following message:

IS INFORMATION SECURITY ESSENTIAL

After encrypting the message, decrypt the following message, using KEYWORD as the keyword:

YRJUW WWRIG JTFUW ERECE LCMKL CIWKR R

For both the encryption and decryption, show your work in a Microsoft Word document to substantiate the result. For this, create two different tables. The first table will have 3 rows and 30 columns. Each column will correspond to an individual character. The first row will correspond to the keyword characters. The second row will correspond to the message to be encrypted. The third row will correspond to the encrypted message.

The second table will have 3 rows and 31 columns. Each column will correspond to an individual character. The first row will correspond to the keyword characters. The second row will correspond to the message to be decrypted. The third row will correspond to the decrypted message.

Solutions

Expert Solution

Encryption
Here we use the following table to encrypt the message

Now we have Plain text IS INFORMATION SECURITY ESSENTIAL
And keyword : KEYWORD
Now first we genrate the key


For generating key, the given keyword is repeated in a circular manner until it matches the length of the plain text.
The keyword "KEYWORD" generates the key KE YWORDKEYWOR DKEYWORD KEYWORDKE

The first letter of the plaintext, I is paired with K, the first letter of the key. So use row I and column K of the Vigenère square, namely .S

Then second latter of the plaintext S, is paired with E, the second latter of the key . So use row S and column E of the Vigenere Square, namely. W

Then Third latter of the plaintext I, is paired with Y, the Third latter of the key . So use row I and column Yof the Vigenere Square, namely. G

The rest of the plaintext is enciphered in a similar fashion.
Plain text: IS INFORMATION SECURITY ESSENTIAL  
Keyword : KE YWORDKEYWOR DKEYWORD KEYWORDKE


The first row will correspond to the keyword characters. The second row will correspond to the message to be encrypted. The third row will correspond to the encrypted message.

Decryption

Decryption is performed by going to the row in the table corresponding to the key, finding the position of the ciphertext letter in this row, and then using the column’s label as the plaintext.

Cipher text is: YRJUW WWRIG JTFUW ERECE LCMKL CIWKR R
Keyword : KEYWO DKEYW RDKEY ORDKE WORDK YWORD E


now first letter of the key K as row and look for the first cipher text letter Y and takes Y's column value we get O as plain text
now take secont latter Of the keyword E and look for the second cipher text letter R and takes R' column value we get N as palin text


The rest of the ciphertext decipher in similar fasion

The first row will correspond to the keyword characters. The second row will correspond to the message to be decrypted and thid row correspond to plain text.

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