Ciphertext

Ciphertext consists of a string of randomised characters that are the encrypted version of a text. It contains the same information as a message in plaintext, but is unreadable by a human or computer without a decryption algorithm. Ciphertext is commonly applied to protect the original message from the loss of sensitive information.

Types of ciphers include block ciphers, public and private key cryptography, substitution ciphers, and transposition ciphers.

A block cipher encrypts data in blocks using a cryptographic key and algorithm to produce a ciphertext. Substitution ciphers, as the name suggests, substitute the characters in a plaintext with other characters from the same set, depending on the key. For instance, A can be substituted with B, and C can be substituted with D, etc.

Contrary to substitution ciphers, transposition ciphers maintain the same characters, but rearrange their order using an algorithm. For example, the phrase ‘a simple example’ can be transposed to ‘ELPMAXE ELPMIS A’.

For private key cryptography, also known as ‘symmetric key algorithm’, the same secret key is used to encrypt and decrypt a message. Public key cryptography uses two keys — one for encryption, and another for decryption. The public key is used to encrypt plaintext into ciphertext, and the private key is used to decrypt the ciphertext into plaintext.