Playfair cipher codec converter:
1) Playfair cipher is a directed graph replacement cipher. It uses an alphabet for encryption and decryption, in which one letter is omitted (usually J is removed from the alphabet), and these letters are arranged in a 5x5 grid to form the original password table.
2) Enter the Playfair encryption key, remove the same characters in the key (delete the same characters that appear afterwards), replace J with I, arrange the remaining keys in a 5x5 network, and press for letters that do not appear. Arrange in order to form a password table.
3) Enter the plaintext to be encrypted and the ciphertext to be decrypted to quickly perform encryption and decryption conversion.