Vigenere Autokey Cipher

Parts of the Central Park Papers are encrypted with the Vigenere Autokey Cipher. This cipher utilizes the Vigenere tableau, otherwise known as the tabula recta. The Vigenere tableau is a table of the 26 alphabets created by starting the alphabet with each of the letters, like this:

cdefghifklmnopqrstuvwxyzab … and so on until

Here is how the cipher works. Suppose this is the enciphered text:

aiha ypr vxjvwx jzhwlv lq grvgtey irrv.

The key is: vaux

Start with the first letter of the key: v. Find v on the left side of the tabula recta. Look in that row for the a, since a is the first letter of the enciphered text. The letter at the top of that column is f. So f is the first letter of the deciphered text.

Using the key vaux, you can decipher the first four letters of the text. Then, the deciphered text is added onto the end of the key. This makes a key of unlimited length.

vaux fin dthese crethi dd enincen tral – key
aiha ypr vxjvwx jzhwlv lq grvgtey irrv – enciphered text
find the secret hidden in central park – deciphered text

Deciphering Program

Deciphering text letter by letter is a laborious process. The “Decipher Text” pages have a program with the enciphered texts from the Central Park Papers already typed in. All you have to do is type in the key and the program will display the deciphered text. Just follow these steps:

1. Pay $10 via PayPal at this link:

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2. Go to the “Decipher Text” page for the text you want to decipher. The password is the merchant’s e-mail address in the PayPal receipt you will receive once you have paid.

Decipher Text 1

Decipher Text 2

Decipher Text 3

Decipher Text 4