Python : Pycrypto RSA public key encryption error

Question

So I've just started experimenting with Pycrypto and wanted to encrypt and decrypt a message, but this code I put together produced some errors.

Here they are:

enc_data = public_key.encrypt 

TypeError: unsupported operand type(s) for pow(): 'str', 'int','int'

ciphertext = cipher.encrypt('Bob')

Traceback (most recent call last):

line 22, in ciphertext = cipher.encrypt('Bob')

File "C:\Anaconda3\lib\site-packages\Crypto\Cipher\PKCS1_OAEP.py", line 50, in encrypt
db = lHash + ps + bchr(0x01) + message

TypeError: can't concat bytes to str

The code:

import Crypto
from Crypto.Hash import SHA256
from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP
from Crypto import Random

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

public_key = key.publickey()

enc_data = public_key.encrypt('Bob', 32)

cipher = PKCS1_OAEP.new(key)
ciphertext = cipher.encrypt('Bob')

The two commands which are meant to encrypt 'Bob' produce these errors, and yes I now that the first way isn't very secure.

Answer 1

In Python 3 there is a difference between strings and bytes. PyCrypto works on bytes, so you need to give it bytes, but "Bob" is a string. You can convert a string a to bytes with a.encode(), which uses a default encoding. If you have another encoding in mind, then you need to specify it.

You can also mark a literal string as bytes by prefixing it with a b. Example: b"Bob".