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The Vigenere Cipher is a well-known cryptographic technique that has been around for ages and has been used to secure sensitive data. Developed in the 16th century by Blaise de Vigenere, it is a polyalphabetic replacement cipher. With the keyword, this cipher is easier to crack since it needs the keyword to both encrypt and decode communications. The Vigenere Cipher will be discussed in this blog article, along with its history, workings, and application in Python, Java, and C.

## History of the Vigenère Cipher

Giovan Battista Bellaso introduced the Vigenere Cipher in his 1553 book Lacifra del Sig. Giovan Battista Bellaso. But Blaise de Vigenere made the cipher better and more well-known. During the Napoleonic Wars, the French deployed the Vigenere Cipher, cracked in the 19th century by Charles Babbage and Friedrich Kasiski. Since then, contemporary cryptography has employed the Vigenere Cipher in many ways.

## How the Vigenère Cipher Works

The Vigenere Cipher encrypts and decrypts communications using a keyword. Up until the message’s length, the keyword is repeated. The message’s letters match each letter in the term. The first letter of the message is encrypted using the first letter of the keyword, if the message is “hello” and the keyword is “key,” for instance. Using the second letter of the keyword, the second letter is used to encrypt the following letters.

A Vigenere Table must be prepared to use the Vigenere Cipher to encrypt a message. The alphabetic characters are arranged in a 26×26 grid in the table. The alphabetic letters are used to define rows and columns. A letter is present in each table cell due to changing the row letter by the column letter. The letter “B” is present in the cell in a row “A” and column “B,” for instance, because of moving row “A” by one.

## Vigenère Cipher Decoder

Knowing the critical word to encrypt the message is necessary to decode a Vigenere Cipher. The message may be decrypted after you know the keyword. The Vigenere Cipher requires that you reverse the technique used to encrypt the communication to decode it. For example, you can change the keywords’ letters instead of the message’s letters.

### How to Use Vigenère Cipher in Programming Languages

Python, Java, and C are just a few computer languages that may be used to implement the Vigenere Cipher. Let’s examine the Vigenere Cipher implementation in these computer languages.

#### a. Vigenere Cipher in Python:

Implementing the Vigenere Cipher in Python is very simple because of Python’s built-in utilities for converting characters to their ASCII codes and vice versa.

#### b. Vigenere Cipher in Java:

The Vigenere Cipher can be implemented in Java similarly to how it can be implemented in Python.

#### c. Vigenere Cipher Program in C:

The Vigenere Cipher needs more work to implement in C since there are no built-in methods for manipulating strings in the language.

#### d. Vigenere Cipher Online:

Several websites offer an online Vigenere Cipher tool that enables users to encrypt and decode communications using the Vigenere Cipher without writing any code. For example, such a website includes https://www.dcode.fr/vigenere-cipher as an illustration.

Enter the plaintext message and the encryption key into the tool, then click “Encrypt” to create the encrypted message. Next, enter the message to be decrypted with the decryption key, then click the “Decrypt” button to produce the unencrypted message.

#### e. Vigenere Cipher Table:

The Vigenere Cipher is used to encrypt and decrypt messages. Its table is often called the Vigenere Square or the Vigenere Tableau. In the table, each row corresponds to a letter from the key, and each column corresponds to a letter from the plaintext.

Locate the row corresponding to the key’s first letter and the column corresponding to the plaintext’s first letter to apply the Vigenere Cipher table. The initial letter of the ciphertext may be seen at the point where the row and column cross. Follow this procedure for each additional letter of the plaintext, using the following letter of the key as the row and, if necessary, wrapping it around to the start of the key.

## Using the Vigenère Cipher Table

To use the Vigenere Cipher, follow these steps:

• Choose a key. The key can be any word or phrase, but it should be a random  combination of letters for added security.
• Write out the message you want to encrypt.
• Write the key underneath the message, repeating the key as many times as necessary to cover the entire message length.
• Find the letter in the Vigenere Cipher table’s first column corresponding to your message’s first letter.
• Find the letter in the table’s first row corresponding to your key’s first letter.
• The letter where the row and column intersect is the encrypted letter. Write this letter down.
•  Repeat steps 4-6 for each letter in the message.

The encrypted message is the series of letters you wrote in step 6.

To decrypt a message encrypted using the Vigenere Cipher, follow the same steps, but use the Vigenere Cipher table in reverse. Instead of finding the letter where the row and column intersect, find the letter in the first row corresponding to the encrypted letter, then find the letter in that column that corresponds to the key letter.

## Conclusion

In conclusion, the 16th-century French cryptographer Blaise de Vigenere developed the Vigenere Cipher, a powerful encryption technique. It is a polyalphabetic cipher, which employs more than one alphabet to encrypt plaintext information. This makes it far more difficult to crack than basic substitution ciphers.

Programming languages like Python, Java, C++, and others may all be used to create the Vigenere Cipher, which is still helpful today. Besides, this cipher allows for simple encoding and decoding of communications using web resources. Finally, the Vigenere Cipher table is another helpful resource that aids in identifying the alphabet to be used throughout the ciphering process.

It is crucial to remember that even though the Vigenere Cipher is a strong encryption technique, it may still be cracked using several methods. As a result, it should be used for more than only protecting sensitive information. Nevertheless, it continues to be a fascinating and historically significant encryption method that has helped current cryptography advance.