Ciphertext

Ciphertext is an encrypted text message created by scrambling plaintext message using cryptographic encryption algorithms. Cryptographic algorithms transform a plaintext message into ciphertext through the application of encryption algorithms and encryption keys. And an entity cannot read, decrypt and access the ciphertext message without the encryption/decryption key. The decryption key, in combination with the cryptographic algorithm, transforms the ciphertext into its original plaintext form. It is used to protect data and sensitive information from being accessed by cybercriminals and anyone else with bad intentions.

Cryptographic algorithms cipher a message into its ciphertext in many different ways, starting from the classical cryptography until the modern quantum computing based quantum cryptography. Some of the most common types of ciphers include the following:

• Substitution: A cipher that replaces characters in the plaintext or original text with different letters, numbers, or other characters.to create the ciphertext. Cryptographic technique that works by replacing an element of plaintext or character with another character.
• Transposition: A cipher, in which characters in the plaintext are rearranged, shifted or change position to form the ciphertext. A cryptographic algorithm, sometimes known as permutation, that works by reordering the elements or characters of the plaintext.
• Monoalphabetic: The feature of a group of ciphers in which a given plaintext character is always mapped into the same ciphertext character on any instances of encryption techniques. Example: Julius Caesar substitution cipher
• Polyalphabetic: A given plaintext character maybe mapped into many different ciphertext characters even in the same plaintext depending on its position in the plaintext message or any other criteria. Example: Playfair cipher, Vigenere cipher
• Block: A cryptographic algorithm that encrypts/decrypts in a fixed-size blocks and produces a block of ciphertext of equal size in recurring manner
• Stream: a cryptographic algorithm that encrypts or decrypts plaintext/ciphertext on one-to-one basis.
• Private Key Cryptography: The sender and receiver must possess a pre-shared secret key through out-of-band channels. It is also called symmetric encryption algorithm.
• Public Key Cryptography: two different key namely public key and private key are used for encryption and decryption processes. Moreover, the send applies the public key to encrypt a message, but the private key is kept secret from the receiver. This is also referred to as asymmetric encryption algorithm.

Common types of ciphertext attacks include the following:

• Ciphertext-only attack
• Chosen ciphertext attack