CORE 139 Methods and Issues in Cryptology Spring 2004

Vigenere Cipher Cracker Tool

Use this tool to crack a Vigenere-encrypted message with a short keyword.

Enter the ciphertext and the keyword length in the appropriate boxes, and click the "initialize" button. Dashes indicate unknown letters in the plaintext and keyword.

To decrypt, guess a letter in the plaintext or the keyword - replace the dash with the desired letter. Click "update keyword" to update the keyword based on the current plaintext or "update plaintext" to update the plaintext based on the current keyword. You can also use "reset keyword" and "reset plaintext" to reset the keyword/plaintext to only what is known given the current state of the other. (The different between "update" and "reset" is that "update" won't change a letter for which the corresponding letter in the other thing is "-", while "reset" will.) To "unguess" a plaintext or keyword letter, replace it with a dash. You can start over from scratch by clicking "initialize".

ciphertext:

keyword length:

Set up the plaintext and keyword to begin decryption.
Reset the plaintext to only the letters known based on the current state of the keyword.
Update the plaintext based on the current state of the keyword. Plaintext letters for which the keyword entry is "-" are not changed.
Reset the keyword to only the letters known based on the current state of the plaintext.
Update the keyword based on the current state of the plaintext.
plaintext:
keyword:


sbridgeman@mail.colgate.edu last updated: --Wed Jan 28 19:50:33 Eastern Standard Time 2004--