In cryptography , ciphertext refers to the output of the encryption process , the process of transforming information ( referred to as plaintext ) using an algorithm ( called cipher ) to make it unreadable to anyone except those who own special information about it , usually referred to as a key . In cryptography , ciphertext ( or cyphertext ) is the result of encryption performed on plaintext using an algorithm , called a cipher . Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it .