algorithm-en.txt

FONCTION CaesarCipher (STRING message, INTEGER key): STRING
    VARIABLE alphabet_length : INTEGER, encrypted_message : STRING, encrypted_character : STRING,
             message_length : INTEGER, first_character : STRING, counter : INTEGER

    key <-- key % alphabet_length

    IF (key < 0) THEN
        key <-- key + alphabet_length
    END IF

    message_length <-- LENGTH(message)
    encrypted_message <-- ""

    FOR counter FROM 1 to message_length DO
        IF (isAlphabetic(message[counter])) THEN
            first_character <-- 'a' OR 'A'
            encrypted_character <-- (message[counter] - first_character + key) % alphabet_length + first_character
            encrypted_message <-- encrypted_message + encrypted_character
        ELSE
            encrypted_message <-- message[counter]
        END IF
    END FOR
END

FONCTION CaesarDecipher (STRING message, INTEGER key): STRING
    RETURN CaesarCipher(message, 26 - key)
END