Implement Hill cipher encryption-decryption in Python.

Hill cipher in Python

import numpy as np

import math

np.keyMatrix = [[0] * 3 for i in range(3)]

messageVector = [[0] for i in range(3)]

cipherMatrix = [[0] for i in range(3)]

plainMatrix = [[0] for i in range(3)]

np.inverseKeyMatrix = [[0] * 3 for i in range(3)]

def getKeyMatrix(key):

  k = 0

  for i in range(3):

    for j in range(3):

      np.keyMatrix[i][j] = ord(key[k]) % 65

      k += 1

def encrypt(messageVector):

  for i in range(3):

    for j in range(1):

      cipherMatrix[i][j] = 0

      for x in range(3):

        cipherMatrix[i][j] += (np.keyMatrix[i][x] * messageVector[x][j])

        cipherMatrix[i][j] = cipherMatrix[i][j] % 26

def HillCipher1(message, key):

  getKeyMatrix(key)

  for i in range(3):

    messageVector[i][0] = ord(message[i]) % 65

  encrypt(messageVector)

  CipherText = []

  for i in range(3):

    CipherText.append(chr(cipherMatrix[i][0] + 65))

  print("Ciphertext: ", "".join(CipherText))

def getInverseKeyMatrix(key):

  getKeyMatrix(key)

  keyMatrix=np.keyMatrix

  from sympy import Matrix

  inverseKeyMatrix = Matrix(keyMatrix).inv_mod(26)

  np.inverseKeyMatrix = np.array(inverseKeyMatrix)

def HillCipher2(message, key):

  getInverseKeyMatrix(key)

  for i in range(3):

    messageVector[i][0] = ord(message[i]) % 65

  decrypt(messageVector)

  PlainText = []

  for i in range(3):

    PlainText.append(chr(int(round(plainMatrix[i][0]) + 65)))

  print("Plaintext: ", "".join(PlainText))

def decrypt(messageVector):

  for i in range(3):

    for j in range(1):

      plainMatrix[i][j] = 0

      for x in range(3):

        plainMatrix[i][j] = plainMatrix[i][j] % 26

        plainMatrix[i][j] += (np.inverseKeyMatrix[i][x] * messageVector[x][j])

      plainMatrix[i][j] = plainMatrix[i][j] % 26

def main():

  message = input("Enter 3 no. of string :")

  message = message.upper()

  key = input("Enter the Key :")

  key = key.upper()

  ch1=int(input("1.Encryption\n2.Decryption\nEnter the choice ::"))

  if ch1 == 1:

    HillCipher1(message, key)

  elif ch1 == 2:

    HillCipher2(message,key)

  else:

    print("Wrong input")

if __name__ == "__main__": 

    main()

OUTPUT

Enter 3 no. of string :sms

Enter the Key :gybnqkurp

1.Encryption

2.Decryption

Enter the choice ::1

Ciphertext:  YIC