from Crypto.Cipher import AES
from Crypto.Hash import SHA256
from Crypto import Random
import os
import sys

def getKey(password):
            hasher = SHA256.new(password.encode('utf-8'))
            return hasher.digest()


def decrypt (key):
    filename = "enim_msg.txt"
    chunksize = 64*1024
    outfile = "en" + filename
    #filesize = str(os.path.getsize(filename)).zfill(16)
    #IV = Random.new().read(16)
    f = open(filename, "r")
    filesize = f.read(16) #Read the first 13 chars
    IV = f.read(16) #Once read filesize read the next 3 chars = IV
    print ("Filesize: "+ str(filesize) + " IV: " + str(IV))

    decryptor = AES.new(key, AES.MODE_CBC, IV)
    outputFile = "finally.txt"

    with open(filename, 'rb') as infile:
        with open(outputFile, 'wb') as outfile:
            #outfile.write(filesize.encode('utf-8'))
            #outfile.write(IV)
            while True:
                chunk = infile.read(chunksize)

                if len(chunk) == 0:
                    break
                elif len(chunk) % 16 != 0:
                    chunk += b' ' * (16 - (len(chunk) % 16))

                outfile.write(decryptor.decrypt(chunk))
password = "sahay"
key = getKey(password)
decrypt(key)