![affine cipher decryption tool affine cipher decryption tool](https://image2.slideserve.com/4431632/the-vigen-re-cipher-l.jpg)
To encode something, you need to pick the 'a' and it must be coprime with the length of the alphabet. In this encrypting example, the plaintext to be encrypted is 'AFFINE CIPHER' using the table mentioned above for the numeric values of each letter, taking a to be 5, b to be 8, and m to be 26 since there are 26 characters in the alphabet being used.
Affine cipher decryption tool mod#
Mathematically, it is represented as e(x) (ax + b) mod m.Decryption is a slightly different formula, d(x) a-1 (x - b) mod m. Therefore the decryption map $D(x)=a^$) for all other solutions, so we get $-55 \equiv -3 \equiv 23 \bmod 26$ is the one and $-3 + 13 = 10$ is the other one, confirming the python script answer. The Affine cipher is a monoalphabetic substitution cipher and it can be the exact same as a standard Caesarian shift when 'a' is 1. This makes my decryption function p (c b) a-1 (mod 26) where b 8, a 7, c number corresponding with cipher character starting from 0, and p is the same for plaintext.
![affine cipher decryption tool affine cipher decryption tool](https://image.slidesharecdn.com/crytography-161203022503/95/crytography-11-638.jpg)
Given two letters of the plaintext 'ZP' corresponding to the ciphertext 'AE' respectively, I have found the key to be (a,b)=(10,10) (modulo 26). I'm trying to decrypt the ciphertext vczkh which I know was encoded using an affine cipher with the equation 7x + 8(mod 26).