This tool can help you encrypt, decrypt, analyze, and crack Vigenère Ciphers. Feel free to use it to analyze the ciphertext from the puzzles each week to discover the key, then use that information to decrypt the puzzle, and encrypt a reply to the @CipherMonkeyTwitter account each week.

To help you get started and a good feel for the tool, here is some Vigenère ciphertext where the key is completely unkown. If you've analyzed everything correctly, you should be able to discover the key, decrypt it, and get to the same plainext as provided:

    Ciphertext: KH IU AJS SWWTSMG HTH OH AJS TGHEVET AQ OWCRGB JQF KB CTLCHIXL GLPTLUGIQU CBD MUQKLGKIS.
     Plaintext: IT IS THE SUPREME ART OF THE TEACHER TO AWAKEN JOY IN CREATIVE EXPRESSION AND KNOWLEDGE.
Vigenere Cipher
Plaintext
Key
Ciphertext

After you input the ciphertext above, you can use the key analysis tool below to try and discover the length of the key, and what the key actually is. The results will show you the Chi-squared statistic for each possible key character. The lower the Chi-squared statistic, the more likely that character is part of the key. For more information on how this actually works, see the Vigenère analysis page for more information. The three buttons will break down the analysis as follows:

  • Analyze: A raw breakdown of the Chi-squared statistic of every alphabetic character A-Z and how it scores against the ciphertext as a possible solution.
  • Column View: A column view of the raw Chi-squared statistic, making it easier to see as a whole group.
  • Summary: The top 5 (lowest Chi-squared scores) candidates for key characters in each position.
Key Analysis

Key Length