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What is Ciphertext?

Alina Farid

Ciphertext

Ciphertext is an algorithm method that replaces plaintext with substitutions:

  • letters are replaced by other letters, but the sequence remains the same
  • simple substitution ciphers replace single letters while the polygraphic operates on more than one letter
  • corresponding characters are written in the past to enable the message to decrypt

Types of ciphertext

The types of ciphertext are:

  • transposition ciphers: This rearranges the order of the letters for a specific algorithm while keeping the letters the same. For example, a message read horizontally could be written vertically to convert it from a simple columnar transposition cipher to a ciphertext

  • Substitution ciphers: The characters, character blocks, and orbits are replaced by similar ones to form a ciphertext. It could be mono-alphabetic or poly-alphabetic depending upon the number of letters being replaced.

  • Polygraphic ciphers: This substitutes groups of letters by replacing each letter with the other letter. This makes the frequency analysis attacks difficult as the frequency of the distribution of letters is masked.

  • Permutation ciphers: This helps with constituting the ciphertext into a permutation of the plaintext by shifting the positions of the plaintext into the regular system.

Uses of ciphertext

  • Ciphers that are used in securing online communications are called symmetric ciphers. Many symmetric cipherssuch as the Transport Layer Security are incorporated into network protocols to encrypt exchanges.

  • Symmetric ciphers help to protect the data in many e-commerce services, WiFis, and mobile telephones.

  • Protocolssuch as the OpenPGP encrypt and authenticate endpoints using asymmetric cryptology.

Example

Caesar cipher is a method in which messages are encoded using the substitution methodletters of the alphabet are replaced by any number of spaces, to yield an encoded alphabet.

For example, if the shift is 3, then A would become D, B would be E, C would become F, and so on until the end of the alphabet when the cycle starts again with X becoming A, Y becoming B, and Z becoming C.

Example of Ciphertext

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