NationMaster - Encyclopedia: Affine cipher

The Affine cipher is a special case of the more general substitution cipher. It is monoalphabetic and symmetric. It is one of the most confusing form of codes devised, the sender can easily determine how many numbers he/she wants to change the code by, but this makes it far harder for the reciever to decode the message. However this form is very useful for warfare purposes. In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the units may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. ...

In affine ciphers the encryption function for a letter is

e (x) = a x + b (mod m)

where,

The decryption function is

d (x) = a - 1 (x - b)(mod m)

where

a - 1

is the multiplicative inverse of

a

in the group $mathbb{Z}_{m}$ Coprime - Wikipedia /**/ @import /skins-1. ... In mathematics, the reciprocal, or multiplicative inverse, of a number x is the number which, when multiplied by x, yields 1. ... Modular arithmetic (sometimes called modulo arithmetic) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value â€” the modulus. ...

This cipher is less secure than a substitution cipher as it is vulnerable to all of the attacks that work against substitution ciphers as well as other attacks. The cipher's primary weakness comes from the fact that if the cryptanalyst can discover (by means of frequency analysis, brute force, guessing or otherwise) the plaintext of two ciphertext characters then the key can be obtained by solving a simultaneous equation. Since we know

a

and

m

are relatively prime this can be used to rapidly discard many "false" keys in an automated system. In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the units may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. ... In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the units may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. ... In mathematics, simultaneous equations are a set of equations where variables are shared. ...

Category: Classical ciphers In cryptography, the ADFGVX cipher was a field cipher used by the German Army during World War I. ADFGVX was in fact an extension of an earlier cipher called ADFGX. Invented by Colonel Fritz Nebel and introduced in March 1918, the cipher was a fractionating transposition cipher which combined a... Atbash is a simple substitution cipher for the Hebrew alphabet. ... An autokey cipher, or self-synchronizing stream cipher, is a cipher which incorporates the message (the plaintext) into the key. ... In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion. ... A book cipher is a cipher in which the key is the identity of a book. ... The action of a Caesar cipher is to move each letter a number of places down the alphabet. ... The Four-square cipher is a manual symmetric encryption technique. ... Hills cipher machine, from figure 4 of the patent In classical cryptography, the Hill cipher is a polygraphic substitution cipher based on linear algebra. ... -1... In classical cryptography, a permutation cipher is a transposition cipher in which the key is a permutation. ... The Pigpen Cipher is a simple substitution cipher exchanging letters for symbols, using a grid. ... The Playfair system was invented by Charles Wheatstone, who first described it in 1854. ... A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets. ... The Reihenschieber was a hand cipher system used by Germany. ... Reservehandverfahren (RHV) (German: Reserve Hand Procedure) was a German Naval World War II hand-cipher system used as a backup method when no working Enigma machine was available[1]. The cipher had two stages: a transposition followed by bigram substitution. ... In classical cryptography, the runnning key cipher is a type of polyalphabetic substitution cipher in which a text, typically from a book, is used to provide a very long key stream. ... In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the units may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. ... In classical cryptography, a transposition cipher changes one character from the plaintext to another (to decrypt the reverse is done). ... In classical cryptography, the trifid cipher is a cipher invented around 1901 by Felix Delastelle, which extends the concept of the bifid cipher to a third dimension, allowing each symbol to be fractionated into 3 elements instead of two. ... The Two-square cipher is a manual symmetric encryption technique. ... The VigenÃ¨re cipher is named for Blaise de VigenÃ¨re (pictured), although Giovan Batista Belaso had invented the cipher earlier. ... In mathematics, physics and signal processing, frequency analysis is a method to decompose a function, wave, or signal into its frequency components so that it is possible to have the frequency spectrum. ... In cryptography, coincidence counting is the technique (invented by William F. Friedman) of putting two texts side-by-side and counting the number of times that a letter appears next to itself in both copies. ... A cryptogram is a short piece of text encrypted with a simple substitution cipher in which each letter is replaced by a different letter. ... In cryptography, the Polybius square is a device invented by the Ancient Greek historian and scholar Polybius, described in Hist. ... This article is about the encryption device; for the Dune character, see Scytale (Dune). ... In cryptography, a straddling checkerboard is a device for converting an alphabetic plaintext into digits whilst simultaneously achieving fractionation (a simple form of information diffusion) and homophony (a simple method for suppressing peaks of the frequency distribution). ... Tabula recta In cryptography, the tabula recta is a square table of alphabets, each one made by shifting the previous one to the left. ...