The disadvantage is the are hard to encode and decode. Ciphers are messages in which letters are represented by letters, words, numbers or symbols. They require knowledge of what cipher was used to decipher. The advantage is the are easy to encipher and decipher. The disadvantage is a determined person can break a cipher easily.
Secret messages are messages that are hidden in some way.
They are usually written in English. That is both an advantage and a disadvantage. It s an advantage because it s easy to write. It s a disadvantage because anyone who finds it can read it. Many ways of hiding messages were used in the Revolutionary War.