Definition of 'Ciphertext'
Definition: Cipher is an algorithm which is applied to plain text to get ciphertext. It is the unreadable output of an encryption algorithm. The term "cipher" is sometimes used as an alternative term for ciphertext. Ciphertext is not understandable until it has been converted into plain text using a key.
Description: Earlier cipher algorithms were performed manually and were entirely different from modern algorithms which are generally executed by a machine. Different types of ciphers exist, some of which are:
Substitution Cipher: This offers an alternative to the plaintext. It is also known as Caesar cipher.
Polyalphabetic Substitution Cipher: In this cipher, a mixed alphabet is used to encrypt the plaintext, but at random points it would change to a different mixed alphabet which indicates the change with an uppercase letter in the Ciphertext.
Transposition Cipher: This cipher is also known as Rail Fence Cipher and is a permutation of the plaintext.
Permutation Cipher: The positions held by plaintext are shifted to a regular system in this cipher so that the ciphertext constitutes a permutation of the plaintext.
Private-key Cryptography: In this cipher, even the attacker is aware of the plaintext and corresponding ciphertext. The sender and receiver must have a pre-shared key. The shared key is kept secret from all other parties and is used for encryption as well as decryption. DES and AES algorithms are examples of this type of cipher. This cryptography is also known as "symmetric key algorithm".
Public-key Cryptography: In this cipher, two different keys - public key and private key - are used for encryption and decryption. The sender uses the public key to perform encryption, whereas the receiver is kept in the dark about the private key. This is also known as asymmetric key algorithm.