Vigenère Cipher Grid

This is a Vigenère Cipher Grid. It lists every Caesar shift and can be used to encrypt messages using a simple polyalphabetic system, choosing a key letter for each letter in the message.

To encrypt a plaintext letter with its key letter, just use those two letters as column and row headings and substitute for the letter in the appropriate cell. For example, if encrypting plaintext letter L using key letter K, look down column L until you get to row K: the letter in this cell is V.

To decide upon a key for each letter, one option is to choose a word or phrase and write this out above the plaintext message, matching each letter in the phrase with one in the message. For example, to encrypt the message "quick send help now" using the keyword "candle," write it out as follows:

Key phrase: C A N D L E C A N D L E C A N D

Plaintext:  Q U I C K S E N D H E L P N O W

Now use encrypt the message, one letter at a time, paring up a letter in the key phrase with the letter underneath it in the plaintext, using the first as a row heading and the second as a row heading. You should get this:

Ciphertext: S U V F V W G N Q K P P R N B Z

You would send this message to your partner, and they need to know what the key phrase is to decrypt it. In order to do so, they will look for each letter in the ciphertext in the column given by the corresponding letter in the key phrase. The row heading indicates what the plaintext letter should be in each position.