How to encrypt and decrypt with variables in Python

Question

My goal is to write a code in Python that do the following: 1.Generate a public key. 2. Hash the public key. 3. Generate a random string. 4. Encrypt & decrypt the random string with the hashed public key.

This is the code I written:

from Crypto.PublicKey import RSA
import random
import string
import hashlib
import base64
from cryptography.fernet import Fernet
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC

def encrypt(plaintext, password):
   f = Fernet(base64.urlsafe_b64encode(
       PBKDF2HMAC(algorithm=hashes.SHA256(), length=32, salt=b'abcd', iterations=1000,
                  backend=default_backend()).derive(password.encode())))
   return f.encrypt(plaintext.encode()).decode()

def decrypt(ciphertext, password):
   f = Fernet(base64.urlsafe_b64encode(
       PBKDF2HMAC(algorithm=hashes.SHA256(), length=32, salt=b'abcd', iterations=1000,
                  backend=default_backend()).derive(password.encode())))
   return f.decrypt(ciphertext.encode()).decode()

def randomString(strlength = 16):   #Random code
   letters = string.ascii_letters
   return ''.join(random.choice(letters) for i in range(strlength))

key = RSA.generate(2048)  # Private key creation
code = 'nooneknows'

privatekey = key.exportKey(passphrase=code, pkcs=8)
publickey = key.publickey().exportKey()

result = hashlib.md5(publickey)  #Hashing the Publickey
publickey = result.digest()

Nonce=randomString()  # Creating Nonce

encrypt((str(Nonce)), password=(str(publickey)))  # Encrypting nonce with hashed pub.key
decrypt((str(encrypt)), password=(str(publickey)))

print("This is the decrption", encrypt)
print("This is the decrption", decrypt)

When I run it, I get the error:

D:\Anaconda3\python.exe C:/Users/AVIV/.PyCharmCE2019.1/config/scratches/test.py
Traceback (most recent call last):
  File "D:\Anaconda3\lib\site-packages\cryptography\fernet.py", line 87, in _get_unverified_token_data
    data = base64.urlsafe_b64decode(token)
  File "D:\Anaconda3\lib\base64.py", line 133, in urlsafe_b64decode
    return b64decode(s)
  File "D:\Anaconda3\lib\base64.py", line 87, in b64decode
    return binascii.a2b_base64(s)
binascii.Error: Incorrect padding

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:/Users/AVIV/.PyCharmCE2019.1/config/scratches/test.py", line 39, in 
    decrypt((str(encrypt)), password=(str(publickey)))
  File "C:/Users/AVIV/.PyCharmCE2019.1/config/scratches/test.py", line 21, in decrypt
    return f.decrypt(ciphertext.encode()).decode()
  File "D:\Anaconda3\lib\site-packages\cryptography\fernet.py", line 74, in decrypt
    timestamp, data = Fernet._get_unverified_token_data(token)
  File "D:\Anaconda3\lib\site-packages\cryptography\fernet.py", line 89, in _get_unverified_token_data
    raise InvalidToken
cryptography.fernet.InvalidToken

Is there a way to solve this error? My guess, is that the issue is with the decoding and encoding to/from bytes. I tried to decode/encode it many times, but always ended up with an error. Also, I guess that it has an issue with the padding, but I couldn't figured how to solve it. I was thinking, maybe the Fernet encryption isn't the right fit for the goals of my project, maybe I should use other encryption/library?

user_14524916 · Answer

You are not actually assigning encrypt to a variable, you are sending in an encrypt function as the argument for the decrypt function. Make this change this at the end of your code:

encrypted = encrypt((str(Nonce)), password=(str(publickey)))  # Encrypting nonce with hashed pub.key
decrypted = decrypt((str(encrypted)), password=(str(publickey)))

print("This is the encrypted", encrypted)
print("This is the decrypted", decrypted)

The output for decrypted will be the Nonce that you encrypted.

How to encrypt and decrypt with variables in Python

1 Answers