Implementing-cryptography-using-python

Chapter 7 ■ Message Integrity 219
import hashlib
import random
import os
from socket import *
from cryptography.fernet import Fernet
key = Fernet.generate_key()
f = Fernet(key)
print ("The key is :", str(key, 'utf-8'))
host = ""
port = 8080
buf = 1024
addr = (host, port)
UDPSock = socket(AF_INET, SOCK_DGRAM)
UDPSock.bind(addr)
print ("Waiting to receive messages...")
def decrypt(ciphertext):
try:
mmac = f.decrypt(ciphertext)
mlen = len(mmac)
m = (mmac[0:mlen - 32])
h = (mmac[-32:])
msg = m,h
except:
msg = ciphertext
return msg
while True:
(data, addr) = UDPSock.recvfrom(buf)
plaintext = decrypt(data)
h = hashlib.md5(plaintext[0])
msg = str(plaintext[0], 'utf-8')
hash = str(plaintext[1], 'utf-8')
print ("Received message: " + msg)
print ("Received digest: " + hash)
print ("Calculated digest: " + h.hexdigest())
if msg == "exit":
break
if msg == 'newkey':
key = Fernet.generate_key()
f = Fernet(key)