# -*- coding: utf8 -*-
from Crypto.Cipher import AES
from Crypto.Hash import SHA256
from os import urandom
import base64
#****************************************************************************************
# Class providing AES-128 CBC with PKCS7 padding cryptographic operations
#****************************************************************************************
class Crypto(object):
#-----------------------------------------------------------
@classmethod
def createKey(cls, outputFormat = "raw"):
if outputFormat == "raw":
return urandom(16) # 128bits AES is an agreed trade off between security and performances
else:
return base64.b64encode(urandom(16))
#-----------------------------------------------------------
@classmethod
def encryptData(cls, clearText, key):
"""Encrypts data with the provided key.
The returned byte array is as follow:
:==============:==================================================:
: IV (16bytes) : Encrypted (data + PKCS7 padding information) :
:==============:==================================================:
"""
# Generate a crypto secure random Initialization Vector
iv = urandom(AES.block_size)
# Perform PKCS7 padding so that clearText is a multiple of the block size
clearText = cls.pad(clearText)
cipher = AES.new(key, AES.MODE_CBC, iv)
return iv + cipher.encrypt(clearText)
#-----------------------------------------------------------
@classmethod
def decryptData(cls, cipherText, key):
"""Decrypt data with the provided key"""
# Initialization Vector is in the first 16 bytes
iv = cipherText[:AES.block_size]
cipher = AES.new(key, AES.MODE_CBC, iv)
return cls.unpad(cipher.decrypt(cipherText[AES.block_size:]))
#------------------------------------------------------------------------
@classmethod
def xor(cls, data, key):
l = len(key)
keyAsInt = map(ord, key)
return bytes(bytearray((
(data[i] ^ keyAsInt[i % l]) for i in range(0,len(data))
)))
#------------------------------------------------------------------------
@classmethod
def convertKey(cls, key, outputFormat = "raw"):
if outputFormat == "raw":
return base64.b64decode(key)
elif outputFormat == "sha256":
return SHA256.new(key).hexdigest()
else:
return base64.b64encode(key)
#------------------------------------------------------------------------
@classmethod
def pad(cls, s):
"""PKCS7 padding"""
return s + (AES.block_size - len(s) % AES.block_size) * chr(AES.block_size - len(s) % AES.block_size)
#------------------------------------------------------------------------
@classmethod
def unpad(cls, s):
"""PKCS7 padding removal"""
return s[:-ord(s[len(s)-1:])]
