Question

Please do not use any existing code, it would be amazing if you could code it yourself

Can i get Playfair Cipher for python 3 that encrypts a message and decrypts a message or exits when prompted by the user, get input from user to encrypt. could you possibly make it as simple as you can without losing functionality.

please include comments, that would help me better understand

Example of PlayFair Cipher:

https://en.wikipedia.org/wiki/Playfair_cipher

Answer 1

PLAYFAIR CIPHER CODE IN PYTHON

# -*- coding: utf-8 -*-
"""
Created on Wed Mar 25 11:59:40 2020

@author: HP
"""

key1=input("Enter key : ")
key1=key1.replace(" ", "")
key1=key1.upper()
def matrix(x,y,initial):
return [[initial for i in range(x)] for j in range(y)]
  
result=list()
for c in key1: #storing key1
if c not in result:
if c=='J':
result.append('I')
else:
result.append(c)
flag=0
for i in range(65,91): #storing other character
if chr(i) not in result:
if i==73 and chr(74) not in result:
result.append("I")
flag=1
elif flag==0 and i==73 or i==74:
pass
else:
result.append(chr(i))
k=0
play_matrix=matrix(5,5,0) #initialize matrix
for i in range(0,5): #making matrix
for j in range(0,5):
play_matrix[i][j]=result[k]
k+=1

def locindex(c): #get location of each character
loc=list()
if c=='J':
c='I'
for i ,j in enumerate(play_matrix):
for k,l in enumerate(j):
if c==l:
loc.append(i)
loc.append(k)
return loc
  
def encrypt(): #Encryption
msg1=str(input("ENTER MSG:"))
msg1=msg1.upper()
msg1=msg1.replace(" ", "")   
i=0
for s in range(0,len(msg1)+1,2):
if s<len(msg1)-1:
if msg1[s]==msg1[s+1]:
msg1=msg1[:s+1]+'X'+msg1[s+1:]
if len(msg1)%2!=0:
msg1=msg1[:]+'X'
print("CIPHER TEXT:",end=' ')
while i<len(msg1):
loc=list()
loc=locindex(msg1[i])
loc1=list()
loc1=locindex(msg1[i+1])
if loc[1]==loc1[1]:
print("{}{}".format(play_matrix[(loc[0]+1)%5][loc[1]],play_matrix[(loc1[0]+1)%5][loc1[1]]),end=' ')
elif loc[0]==loc1[0]:
print("{}{}".format(play_matrix[loc[0]][(loc[1]+1)%5],play_matrix[loc1[0]][(loc1[1]+1)%5]),end=' ')
else:
print("{}{}".format(play_matrix[loc[0]][loc1[1]],play_matrix[loc1[0]][loc[1]]),end=' ')
i=i+2

def decrypt(): #decryption
msg1=str(input("ENTER CIPHER TEXT:"))
msg1=msg1.upper()
msg1=msg1.replace(" ", "")
print("PLAIN TEXT:",end=' ')
i=0
while i<len(msg1):
loc=list()
loc=locindex(msg1[i])
loc1=list()
loc1=locindex(msg1[i+1])
if loc[1]==loc1[1]:
print("{}{}".format(play_matrix[(loc[0]-1)%5][loc[1]],play_matrix[(loc1[0]-1)%5][loc1[1]]),end=' ')
elif loc[0]==loc1[0]:
print("{}{}".format(play_matrix[loc[0]][(loc[1]-1)%5],play_matrix[loc1[0]][(loc1[1]-1)%5]),end=' ')
else:
print("{}{}".format(play_matrix[loc[0]][loc1[1]],play_matrix[loc1[0]][loc[1]]),end=' ')
i=i+2

while(1):
choice=int(input("\n 1.Encryption \n 2.Decryption: \n 3.EXIT"))
if choice==1:
encrypt()
elif choice==2:
decrypt()
elif choice==3:
exit()
else:
print("Choose correct choice")

OUTPUT

Enter key : play fair example

1.Encryption
2.Decryption:
3.EXIT

ENTER MSG:hide the gold in the tree stump
CIPHER TEXT: BM OD ZB XD NA BE KU DM UI XM MO UV IF

1.Encryption
2.Decryption:
3.EXIT