- Type or paste enchiphered text into the textbox on the right. A histogram
to the left shows the relative frequency of each of the letters in the text.
(If the histograph does not appear immediately on pasting, press the "Count" button.)
- If you know that the ciphertext was made using a letter-substitution
cipher from English plaintext, then information about letter frequencies
can help you identify key letters. Usually "E" is the most common letter
in English text, with "A", "O" and "T" running next. So the chances are that
"E" has been replaced by whichever letter is the most common in the
- Use the Affine Cipher Calculator to experiment with
the results of various possible substitutions. Once you have identified
which letters have been substituted a few key letters such as "A", "E", "O" and "T",
then even a partial deciphering of the message should enable you to guess the rest.