bigraphic
As bigraphisch (also bigrafisch ; from Latin : bi = "two" and Greek : γράφει ( graphei "write") =) is in cryptography , ie in the branch of science of cryptology , which deals with the secret writing is concerned, an encryption , especially a Substitution is the term used to describe the plaintext in which the plaintext is broken down into two characters, i.e. into pairs of characters, and one or more ciphertext characters are assigned to each plaintext pair . This is also known as bigram substitution .
A distinction is made between monopartite , bipartite and tripartite bigraphic substitutions, depending on whether each pair of plaintext characters is converted into a single, two or three ciphertext characters during encryption .
Another distinguishing feature is whether only a single or several (many) different secret alphabets are used for encryption. In the first case one speaks of a monoalphabetic substitution, otherwise of a polyalphabetic monographic substitution.
A classic example of a bigraphic monoalphabetic bipartite substitution is the Playfair method .
In contrast to the bigraphic substitutions, there are the monographic substitutions, in which the plain text is not broken down into pairs of characters but into individual characters and thus encrypted. A generalization of bigraphic substitution are polygraphic substitutions (also: polygram substitution), in which the plain text is broken down into several (many) characters for encryption.
See also
literature
- Friedrich L. Bauer : Deciphered Secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, ISBN 3-540-67931-6 .