Symmetric Encryption

Symmetric Encryption AES256 Algorithm (Python)

#How To - perform a symmetric encryption using AES256 algorithm in Python

##Step 1 - use terminal and the command <pip install pycryptodome> to install a library that provides access to the AES256 algorithm.

##Step 2 - create an AES256 key and save it.
import os

key = os.urandom(32)
with open('key.bin', 'wb') as f:
    f.write(key)
    print(key) #not sure if I need this step but I want to see the output


##Step 3 - create a string to test encryption.
from Crypto.Cipher import AES

with open('key.bin', 'rb') as f:
    key = f.read()

cipher = AES.new(key, AES.MODE_EAX)
plaintext = b'Hello, world!'
ciphertext, tag = cipher.encrypt_and_digest(plaintext)
print(plaintext) #to see the output


##Step 4 - perform AES256 symmetric decryption on the cipher text to get the original text.
from Crypto.Cipher import AES

with open('key.bin', 'rb') as f:
    key = f.read()

cipher = AES.new(key, AES.MODE_EAX, nonce=cipher.nonce)
plaintext = cipher.decrypt(ciphertext)
print(ciphertext) #to see the output


##Step 5 - use the command <assert> to check if decrypted data is the same as the original string.
assert plaintext == b'Hello, world!'
print (plaintext) #to see the output

How do I use python to perform symmetric encryption operation in the order below:

• Find the right library that provide you with access to AES256 algorithm.
• Create and save your AES256 key.
• Create a string to test encryption.

Perform AES256 symmetric encryption on the data to get cipher text.

• Use AES256 symmetric decryption on the cipher text to get original text.
• Use assert to check if decrypted data is the same as original string.

AWS re/Start Course Homework, 10 November 2023

Further Reading. - Cryptography
https://pymotw.com/3/hmac/index.html
https://pymotw.com/3/hashlib/index.html