Substitution Cipher Tool

To decrypt using a known ciphertext alphabet, enter the ciphertext message and the ciphertext alphabet and click "decrypt".

To decrypt using an unknown ciphertext alphabet, enter the ciphertext message and click "decrypt". Unknown plaintext letters will be shown as dashes. Enter guesses for cipher alphabet letters in the appropriate alphabet boxes and click "decrypt" to update the plaintext. You can also enter guesses for plaintext letters directly in the plaintext box; click "update alphabet" to update the cipher alphabet accordingly. The cipher alphabet letter will be shown as "*" if it cannot be determined because there are contradictory entries in the plaintext. Unguess plaintext letters by replacing them with a dash. Use "reset alphabet" to adjust the cipher alphabet to just those letters which can be determined from the current plaintext, and "clear alphabet" to remove all plaintext-ciphertext letter associations from the alphabet.