Encryption is the process of encoding information so that it can be kept secure and confidential. The term encryption is derived from the Greek word kryptos, meaning 'HIDDEN.' A CIPHER is a type of encryption in which plaintext is converted into ciphertext using an algorithm. Ciphertext is unreadable until it is decrypted using a key. Common ciphers include the Caesar CIPHER, the Vigenère CIPHER, and the Enigma machine.