Monday, May 22, 2017

The pycrypto python module - part 001.

This python module name pycrypto is a collection of Python Cryptography Toolkit.
This python module has been created by Andrew Kuchling and now maintained by Dwayne C. Litzenberger.
Let's install under Windows 10 OS using Command Prompt (Admin) shell.
C:\WINDOWS\system32>cd ..

C:\Windows>cd ..

C:\>cd Python27\Scripts

C:\Python27\Scripts>pip install pycrypto
Requirement already satisfied: pycrypto in c:\python27\lib\site-packages
Some info and help under python shell can be see using this:
C:\Python27>python.exe
Python 2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:42:59) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import Crypto
>>> dir(Crypto)
['__all__', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__', 
'__revision__', '__version__', 'version_info']
>>> help(Crypto)
Help on package Crypto:

NAME
    Crypto - Python Cryptography Toolkit

FILE
    c:\python27\lib\site-packages\crypto\__init__.py

DESCRIPTION
    A collection of cryptographic modules implementing various algorithms
    and protocols.

    Subpackages:

    Crypto.Cipher
     Secret-key (AES, DES, ARC4) and public-key encryption (RSA PKCS#1) algorithms    Crypto.Hash
     Hashing algorithms (MD5, SHA, HMAC)
    Crypto.Protocol
     Cryptographic protocols (Chaffing, all-or-nothing transform, key derivation
     functions). This package does not contain any network protocols.
    Crypto.PublicKey
     Public-key encryption and signature algorithms (RSA, DSA)
    Crypto.Signature
     Public-key signature algorithms (RSA PKCS#1)
    Crypto.Util
     Various useful modules and functions (long-to-string conversion, random number
     generation, number theoretic functions)

PACKAGE CONTENTS
    Cipher (package)
    Hash (package)
    Protocol (package)
    PublicKey (package)
    Random (package)
    SelfTest (package)
    Signature (package)
    Util (package)
    pct_warnings

DATA
    __all__ = ['Cipher', 'Hash', 'Protocol', 'PublicKey', 'Util', 'Signatu...
    __revision__ = '$Id$'
    __version__ = '2.6.1'

VERSION
    2.6.1
Let's test some examples with this python module.
First example come with encrypt and decrypt message based one key.
The key also is need to be one encryption key and fix to key32.
The iv will not be specified by user, it will be generated and then encrypted with RSA.
NEVER make the IV constant and unique, it must be unique for every message.
Let's see the example source code:
from Crypto.Cipher import AES
from Crypto import Random
def encrypt(key32,message):
    cipher=AES.new(key32,AES.MODE_CFB,iv)
    msg=cipher.encrypt(message)
    print(msg)
    return msg
def decrypt(key32,msg):
    dec=AES.new(key32,AES.MODE_CFB,iv)
    return dec.decrypt(msg).decode('ascii')
if __name__=='__main__':
    global iv
    iv=Random.new().read(AES.block_size)
    key='free-tutorials.org'
    key32 = "".join([ ' ' if i >= len(key) else key[i] for i in range(32) ])
    message='another website with free tutorials'
    enc =encrypt(key32, message)
    print enc
    print(decrypt(key32,enc))
The result output is this:
ᄚ Cᆪ゚2 ᄊÕ|ýXÍ ᄇNäÇ3ヨ゙Lマᆱuï: ù メNᄚm
ᄚ Cᆪ゚2 ᄊÕ|ýXÍ ᄇNäÇ3ヨ゙Lマᆱuï: ù メNᄚm
another website with free tutorials

Another more simplistic example:
from Crypto.Cipher import AES
from Crypto import Random
key = b'Sixteen byte key'
iv = Random.new().read(AES.block_size)
cipher = AES.new(key, AES.MODE_CFB, iv)
msg = iv + cipher.encrypt(b'Attack at dawn')
See the output of variables:
>>> print key
Sixteen byte key
>>> print iv
ÔÄ▀DÒ ÕØ} m║dÕ╚\
>>> print cipher.encrypt(b'Attack at dawn')
åÌ£┴\u\ÍÈSÕ╦╔.
Using MD5 example:
>>> from Crypto.Hash import MD5
>>> MD5.new('free text').hexdigest()
'be9420c1596a781119c53a9933a8234f'
Using RSA key example:
>>> from Crypto.PublicKey import RSA
>>> from Crypto import Random
>>> rng = Random.new().read
>>> RSAkey = RSA.generate(1024, rng)
>>> public_key = RSAkey.publickey()
>>> print public_key
<_RSAobj @0x3650b98 n(1024),e>
>>> enc_data = public_key.encrypt('test data', 32)[0]
>>> print enc_data
H +îÕÊ ÙH:?ª2S½Fã0á! f¬ = ·+,Í0r³┐o·¼ÉlWy¿6ôên(£jê¿ ╦çª|*°q Ò4ì┌çÏD¦¿╝û╠╠MY¶ïzµ>©a}hRô ]í;
_[v¸¤u:2¦y¾/ ²4R╩HvéÌ'÷Ç)KT:P _>> dec_data = RSAkey.decrypt(enc_data)
>>> print dec_data
test data 
Encrypted and decrypted output texts may look different depending on how encoded the used text editor or python language.



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