The Black Chamber

If you want to crack a message encrypted with the substitution cipher, then here is an interactive tool.

  1. Cut and paste your enciphered message in the box marked cipher text, or click on random ciphertext if you do not have a message to hand.
  2. Then, click on the button labelled 'Frequency of Individual Letters'.
  3. The letter that appears most frequently probably represents an E. Enter this letter in the empty box above E in the row labelled 'Plaintext Alphabet'.
  4. All these letters will be transformed into 'E's and you have made the first step towards cracking the message.
  5. Look at other frequent letters and match them to frequent letters in English. Before trying to crack a message, you might want to note down the most frequent letters, which are outlined in the letter frequencies page.
  6. You will soon be able to spot words and guess other letters by their context.
  7. This codebreaking page has more sophisticated elements at the bottom of the page. For example, you can also examine the frequency of paired letters and compare them to the frequency of paired letters in English, or you can look at repeated letters, or the vowel trowel.
Good Luck!

Random Ciphertext Pick Ciphertext Show Solution Clear Alphabet




Frequency of Individual Letters
Frequency of Repeated Letters
Frequency of Pairs of Letters
Vowel Trowel
Clear Boxes