Introduction

Cryptography is used for security purposes. There are not so many examples of Encryption/Decryption in Python using IDEA encryption MODE CTR. Aim of this documentation :

Extend and implement of the RSA Digital Signature scheme in station-to-station communication. Using Hashing for integrity of message, that is SHA-1. Produce simple Key Transport protocol. Encrypt Key with IDEA encryption. Mode of Block Cipher is Counter Mode

Remarks

Language Used: Python 2.7 (Download Link: https://www.python.org/downloads/ )

Library Used:

*PyCrypto (Download Link: https://pypi.python.org/pypi/pycrypto )

*PyCryptoPlus (Download Link: https://github.com/doegox/python-cryptoplus )

Library Installation:

PyCrypto: Unzip the file. Go to the directory and open terminal for linux(alt+ctrl+t) and CMD(shift+right click+select command prompt open here) for windows. After that write python setup.py install (Make Sure Python Environment is set properly in Windows OS)

PyCryptoPlus: Same as the last library.

Tasks Implementation: The task is separated into two parts. One is handshake process and another one is communication process. Socket Setup:

• As the creating public and private keys as well as hashing the public key, we need to setup the socket now. For setting up the socket, we need to import another module with “import socket” and connect(for client) or bind(for server) the IP address and the port with the socket getting from the user.

**----------Client Side----------**

   server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
   host = raw_input("Server Address To Be Connected -> ")
   port = int(input("Port of The Server -> "))
   server.connect((host, port))

**----------Server Side---------**

   try:
   #setting up socket
   server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)     
   server.bind((host,port))
   server.listen(5)
   except BaseException: print "-----Check Server Address or Port-----"

“ socket.AF_INET,socket.SOCK_STREAM” will allow us to use accept() function and messaging fundamentals. Instead of it, we can use “ socket.AF_INET,socket.SOCK_DGRAM” also but that time we will have to use setblocking(value) .

Handshake Process:

• (CLIENT)The first task is to create public and private key. To create the private and public key, we have to import some modules. They are : from Crypto import Random and from Crypto.PublicKey import RSA. To create the keys, we have to write few simple lines of codes:

random_generator = Random.new().read
    key = RSA.generate(1024,random_generator) 
    public = key.publickey().exportKey()

random_generator is derived from “from Crypto import Random” module. Key is derived from “from Crypto.PublicKey import RSA” which will create a private key, size of 1024 by generating random characters. Public is exporting public key from previously generated private key.

• (CLIENT)After creating the public and private key, we have to hash the public key to send over to the server using SHA-1 hash. To use the SHA-1 hash we need to import another module by writing “import hashlib” .To hash the public key we have write two lines of code: