The sender uses the public key to perform the encryption, but the private key is kept secret from the receiver. In this cipher, two different keys - public key and private key - are used for encryption and decryption. This cryptography is also known as 'symmetric key algorithm.' The shared key is kept secret from all other parties and is used for encryption, as well as decryption. In this cipher, the sender and receiver must have a pre-shared key. In this cipher, the positions held by plaintext are shifted to a regular system so that the ciphertext constitutes a permutation of the plaintext. This masks the frequency distribution of letters, making frequency analysis attacks much more difficult. Substituting one letter for another letter, a polygraphic cipher performs substitutions with two or more groups of letters. For instance, in a simple columnar transposition cipher, a message might be read horizontally but would be written vertically to produce the ciphertext.

Unlike substitution ciphers that replace letters with other letters, transposition ciphers keep the letters the same, but rearrange their order according to a specific algorithm. For instance, the letter A may be encoded as the letter K for part of the message, but later it might be encoded as the letter W. A more complex substitution using a mixed alphabet to encrypt each bit, character or character block of a plaintext message.For example, if the letter A is enciphered as the letter K, this will be the same for the entire message. A single alphabet is used to encrypt the entire plaintext message.A substitution cipher may be monoalphabetic or polyalphabetic : Substitution ciphers. Replace bits, characters, or character blocks in plaintext with alternate bits, characters or character blocks to produce ciphertext.

There are various types of ciphers, including: However, it refers to the method of encryption rather than the result. The term cipher is sometimes used as a synonym for ciphertext. The decryption cipher is an algorithm that transforms the ciphertext back into plaintext. Ciphertext can't be read until it has been converted into plaintext (decrypted) with a key. Protocols such as the OpenPGP encrypt and authenticate endpoints using asymmetric cryptology.Ĭaesar cipher is a method in which messages are encoded using the substitution method letters of the alphabet are replaced by any number of spaces, to yield an encoded alphabet.įor 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.Ciphertext is encrypted text transformed from plaintext using an encryption algorithm. Symmetric ciphers help to protect the data in many e-commerce services, WiFis, and mobile telephones. Many symmetric ciphers such as the Transport Layer Security are incorporated into network protocols to encrypt exchanges. 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.Ĭiphers that are used in securing online communications are called symmetric ciphers. This makes the frequency analysis attacks difficult as the frequency of the distribution of letters is masked. This substitutes groups of letters by replacing each letter with the other letter. It could be mono-alphabetic or poly-alphabetic depending upon the number of letters being replaced. Substitution ciphers: The characters, character blocks, and orbits are replaced by similar ones to form a ciphertext. This rearranges the order of the letters for a specific algorithm while keeping the letters the same.įor example, a message read horizontally could be written vertically to convert it from a simple columnar transposition cipher to a ciphertext corresponding characters are written in the past to enable the message to decrypt.simple substitution ciphers replace single letters while the polygraphic operates on more than one letter.letters are replaced by other letters, but the sequence remains the same.Ciphertext is an algorithm method that replaces plaintext with substitutions:

Cipher text