Vigenere Cipher

A Vigenere Cipher is an extended Caesar Cipher where a message is encrypted using various Caesar shifted alphabets.

The following table can be used to encode a message: Vigenere Square

Encryption

For example, encrypting the text SUPERSECRET with CODE would follow this process:

  1. CODE gets padded to the length of SUPERSECRET so the key becomes CODECODECOD
  2. For each letter in SUPERSECRET we use the table to get the Alphabet to use, in this instance row C and column S
  3. The ciphertext's first letter then becomes U
  4. We eventually get UISITGHGTSW

Decryption

  1. Go to the row of the key, in this case C
  2. Find the letter of the cipher text in this row, in this case U
  3. The column is the first letter of the decrypted ciphertext, so we get S
  4. After repeating this process we get back to SUPERSECRET