Cryptography with Python - Affine Cipher

Affine Cipher is the combination of Multiplicative Cipher and Caesar Cipher algorithm. The basic implementation of affine cipher is as shown in the image below −

In this chapter, we will implement affine cipher by creating its corresponding class that includes two basic functions for encryption and decryption.

Example - Using Affine Cipher

You can use the following code to implement an affine cipher −

main.py

class Affine(object):
   DIE = 128
   KEY = (7, 3, 55)
   def __init__(self):
      pass
   def encryptChar(self, char):
      K1, K2, kI = self.KEY
      return chr((K1 * ord(char) + K2) % self.DIE)
		
   def encrypt(self, string):
      return "".join(map(self.encryptChar, string))
   
   def decryptChar(self, char):
      K1, K2, KI = self.KEY
      return chr(KI * (ord(char) - K2) % self.DIE)
   
   def decrypt(self, string):
      return "".join(map(self.decryptChar, string))
affine = Affine()
print(affine.encrypt('Affine Cipher'))
print(affine.decrypt('JMMbFcXb[F!'))

Output

You can observe the following output when you implement an affine cipher −

JMMbFcXb[F!
Affie Ciher

The output displays the encrypted message for the plain text message Affine Cipher and decrypted message for the message sent as input abcdefg.