Implementing-cryptography-using-python

Chapter 5 ■ Stream Ciphers and Block Ciphers 155
# generate a random key that has 32 bits
key = os.urandom(32)
print('The key that will be used is {}'.format(key))
print()
plaintext = b'Attack the yellow submarine.'
print('The plaintext is {}'.format(plaintext))
print()
# generate a random IV that has 12 bits
iv = os.urandom(12)
cip = ChaCha20Poly1305(key)
ciphertext = cip.encrypt(iv, plaintext)
print(ciphertext)
print()
plaintext = cip.decrypt(iv, ciphertext)
print(plaintext)
print()
The preceding use of the ChaCha20Poly1305 library should produce output
similar to Figure 5.4.
Figure 5.4: ChaCha20Poly1305
An alternative library that you may find helpful as well is the Crypto library.
You can import ChaCha20 from the Crypt.Cipher library:
import json
from base64 import b64encode
from Crypto.Cipher import ChaCha20
from Crypto.Random import get_random_bytes
plaintext = b'Attack at dawn'
key = get_random_bytes(32)
cipher = ChaCha20.new(key=key)
ciphertext = cipher.encrypt(plaintext)
nonce = b64encode(cipher.nonce).decode('utf-8')
ct = b64encode(ciphertext).decode('utf-8')