Sender.py

#Security Goals
#Sender Program
import socket, hashlib,time


symmetric_key = 3    
def encrypt_data(message):
    print("".center(80,"*"))
    print("Encrypting data...")
    t=""
    print(message)
    #message = message.lower()
    for i in message:
        if i.isupper():
            alphabet = chr((ord(i)+symmetric_key-65)%26+65)
        elif i.islower():
            alphabet = chr((ord(i)+symmetric_key-97)%26+97)
        #elif i.isnumeric():
            #alphabet = chr((ord(i)+symmetric_key-48)%10+48)
        else:
            alphabet = chr(ord(i)+symmetric_key)
            
        t=t+alphabet
    #message
   
    return t
    
def hash_data(messageToSent):
    print("".center(80,"*"))
    print("Computing the hash of the data...")
    hashedData = hashlib.md5(messageToSent.encode())
    hashedDataByte = hashedData.hexdigest()
    return hashedDataByte

def makeConnection():
    #creating a socket object
    senderSocket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

    #Get local machine name
    host=socket.gethostname()
    port=9999

    #bind to the port
    senderSocket.bind((host,port))
    print("Socket binded to ",port)

    #queue upto 5 connection requests
    senderSocket.listen(5)
    print("Socket is listening for client connections")

    #establishing a connection with client
    clientSocket,address = senderSocket.accept()
    print("Got a connection from client with address ",str(address))

    #normal case
    messageToSent = "This is a data to be sent to the receiver 123."
    #calling functions to secure data
    hashedData = hash_data(messageToSent)
    encryptedData_Key = encrypt_data(messageToSent)
    #dataToSent = encryptedData_Key[0] + "-" + encryptedData_Key[1]
    dataToSent= '{"Message":"'+encryptedData_Key+'","Key":"'+str(symmetric_key)+'","Hash":"'+str(hashedData)+'"}'
    #Sending Data Packet to Client
    clientSocket.send(dataToSent.encode('ascii'))
    print("".center(80,"*"))
    print("Data is sent successfully")
    
    #key modified case
    dataToSent= '{"Message":"'+encryptedData_Key+'","Key":"'+""+'","Hash":"'+str(hashedData)+'"}'
    #Sending Data Packet to Client
    clientSocket.send(dataToSent.encode('ascii'))
    print("".center(80,"*"))
    print("Data is sent successfully")
    print("".center(80,"*"))

    #connection closed case
    dataToSent= '{"Message":"'+""+'","Key":"'+""+'","Hash":"'+""+'"}'
    time.sleep(10)
    clientSocket.send(dataToSent.encode('ascii'))
    clientSocket.close()
    print("Connection closed...\nThank you")

    
print("".center(80,"*"))
print("\t\t\t\t\tSender")
print("".center(80,"*"))
makeConnection()