The Vigenère cipher can also be described and then decrypted algebraically, by assigning each letter from A to Z a value from 0 to 25, with addition being performed modulo 26. The vertical column where that cipher text letter is located reveals the plaintext letter I. In the B row, find the corresponding cipher text letter J.
Using the tabula recta, find the row that corresponds to the first letter in your secret key text- in our case, B. First repeat the secret key so its length matches the cipher text. You can work backwards using the tabula recta.
If you have the secret key, decrypting is as easy as encrypting.
SUBSTITUTION CIPHER DECRYPTION TOOL HOW TO
Once you’ve mastered the tabula recta, the encryption process is easy! How to Decrypt it You can use this cipher for short or long messages.
Once you’ve done that for every character, your final encrypted text should look like this: For this example, the first letter of the encrypted cipher text is J. Take one letter from the plaintext group and a letter from the secret key group (we’re going to start with I and B), and find the entry in the tabula recta where the row and column intersect. Once the two lines are split into five-letter groups, start encrypting. The next step is repeating the secret key enough times so its length matches the plain text. Let’s take this plaintext phrase as an example:Īfter finalizing the plaintext, the person encrypting would then pick a secret key, which would help encrypt and decrypt the message. This continues for the entire square.Īlso, other alphabets than the English alphabet can be used in a similar way to construct a tabula recta. Once B moves to the front, A moves down to the end. Each row of the square has the 26 letters of the Latin alphabet, shifted one position to the right in a cyclic way as the rows progress downwards. The tabula recta typically contains the 26 letters of the Latin alphabet from A to Z along the top of each column, and repeated along the left side at the beginning of each row. In the Vigenère cipher, a message is encrypted using a secret key, as well as an encryption table (called a Vigenere square, Vigenere table, or tabula recta). If the message was right shifted by 4, each A would become E, and each S would become W. The Caesar cipher encrypts by shifting each letter in the plaintext up or down a certain number of places in the alphabet. The Vigenère cipher is a polyalphabetic substitution cipher that is a natural evolution of the Caesar cipher. Standard mode is the most common, but if you don't know the mode, you should try both. Note: Auto Solve will try in the mode you select (Standard Mode or Autokey mode). In case a specific letter (for instance X) is used as word separator, set it to Substitute. In most cases it should be set to Automatic.