Four-Square Cipher
The Four-Square cipher is a polygraphic substitution cipher. It replaces each plaintext pair of letters by another two letters, based on the four encryption tables. The tables are created based on two keywords (passwords) provided by the user.
For more detailed description of the Four-Square cipher, please visit Crypto-IT webpage.
Password for upper-right table
Enter the first secret password. It will be used for creating the upper-right table used for actual encryption/decryption. If no password is provided, the upper-right table will be sorted alphabetically.
Password for lower-left table
Enter the second secret password. It will be used for creating the lower-left table used for actual encryption/decryption. If no password is provided, the lower-left table will be sorted alphabetically.
Input Message
Enter a message you want to encrypt/decrypt. After that, click the correct button below.
Formatted Input Message
Preview the message that actually will be processed. Note, that only letters that are present in the tables below will be encrypted/decrypted.
Parameters:
Treat J as I
Ignore Q
Ignore X Choose how to deal with the 26th letter of the Latin alphabet.
Treat J as I
Ignore Q
Ignore X Choose how to deal with the 26th letter of the Latin alphabet.
| A | B | C | D | E |
| F | G | H | I | K |
| L | M | N | O | P |
| Q | R | S | T | U |
| V | W | X | Y | Z |
| A | B | C | D | E |
| F | G | H | I | K |
| L | M | N | O | P |
| Q | R | S | T | U |
| V | W | X | Y | Z |
| A | B | C | D | E |
| F | G | H | I | K |
| L | M | N | O | P |
| Q | R | S | T | U |
| V | W | X | Y | Z |
| A | B | C | D | E |
| F | G | H | I | K |
| L | M | N | O | P |
| Q | R | S | T | U |
| V | W | X | Y | Z |
Output Message
The result of encryption/decryption. The output text may contain an additional letter, added if the original input message length is odd. Note, that only letters appear in the output text, all other characters were removed.
