what is vigenere cipher course hero

The vigenere cipher is an algorithm of encrypting an alphabetic text that uses a series of interwoven caesar ciphers. It is based on a keyword's letters. It is an example of a polyalphabetic substitution cipher.

Full Answer

What is Vigenere cipher?

Last Updated : 16 Jun, 2021 Vigenere Cipher is a method of encrypting alphabetic text. It uses a simple form of polyalphabetic substitution. A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets.The encryption of the original text is done using the Vigenère square or Vigenère table.

How do you decode a Vigenere cipher without the key?

Decoding a Vigenere cipher without the key is very difficult - you first need to find the length of the key, before identifying what the key is and then finally deciphering the message. Because it is so difficult, your best bet is to try and work out what the key is in other ways.

Why does the cipher use a different alphabet for each row?

At different points in the encryption process, the cipher uses a different alphabet from one of the rows. The alphabet used at each point depends on a repeating keyword.

What is Vigenère cipher method?

Vigenère cipher, type of substitution cipher used for data encryption in which the original plaintext structure is somewhat concealed in the ciphertext by using several different monoalphabetic substitution ciphers rather than just one; the code key specifies which particular substitution is to be employed for ...

Where is Vigenère cipher used?

A good example of the Vigenère Cipher is the Confederate Cipher Disk that was used as a field cipher during the American Civil War (1861-1865).

When was the Vigenère cipher used?

First documented in 1553, the Vigenère cipher is thought to have remained unbroken until 1863. The Vigenère cipher was often referred to as “the unbreakable cipher” by many, including the mathematician Charles Lutwidge Dodgson, also known by his pen name Lewis Carroll.

Is Vigenère cipher easy to crack?

A Vigenère cipher is difficult to crack using brute-force because each letter in a message could be encoded as any of the 26 26 26 letters. Because the encoding of the message depends on the keyword used, a given message could be encoded in 2 6 k 26^k 26k ways, where k k k is the length of the keyword.

How was Vigenère cipher broken?

Without the keyword the primary method of breaking the Vigenère cipher is known as the Kasiski test, after the Prussian major who first published it. The first stage is determining the length of the keyword.

What is Vigenere table?

The encryption of the original text is done using the Vigenère square or Vigenère table. The table consists of the alphabets written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous alphabet, corresponding to the 26 possible Caesar Ciphers.

How many keys are there in Vigenere cipher?

95,428,956,661,682,176 possibleThere are 95,428,956,661,682,176 possible 12-letter keys, but there are only about 1,800 12-letter words in our dictionary file.

What is a Vigenere cipher?

Vigenère Cipher. Vigenere Cipher is a method of encrypting alphabetic text. It uses a simple form of polyalphabetic substitution. A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets .The encryption of the original text is done using the Vigenère square or Vigenère table.

Who contributed to the GeeksForGeeks article?

This article is contributed by Ayush Khanduri. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to [email protected]. See your article appearing on the GeeksforGeeks main page and help other Geeks.

What is a Vigenere cipher?

Vigenere Cipher. A Vigenere Cipher is a cipher which is encrypted using a key, and which can only be decoded by using a Vigenere Square. This is a Vigenere Square:

How to decode Vigenere without key?

Decoding a Vigenere cipher without the key is very difficult - you first need to find the length of the key, before identifying what the key is and then finally deciphering the message. Because it is so difficult, your best bet is to try and work out what the key is in other ways.