# Understanding RSA and AES Encryption in Python

We're dedicated to helping you understand the intricacies of data security. In this comprehensive guide, we'll walk you through the concepts of RSA and AES encryption using Python, two powerful encryption techniques that play a crucial role in safeguarding sensitive information.

## RSA Encryption:

RSA (Rivest–Shamir–Adleman) is an asymmetric encryption algorithm that utilizes a pair of keys: a public key for encryption, a private key for decryption, and can be a topic where you might need help with Python assignment. Our step-by-step Python implementation of RSA encryption will demystify the process for you.

``````python # Step 1: Import necessary libraries import random import math # Step 2: Define functions for RSA key generation def generate_prime(bits): while True: n = random.getrandbits(bits) if n % 2 != 0 and is_prime(n): return n def is_prime(n): if n <= 1: return False for i in range(2, int(math.sqrt(n)) + 1): if n % i == 0: return False return True def extended_gcd(a, b): if a == 0: return b, 0, 1 g, y, x = extended_gcd(b % a, a) return g, x - (b // a) * y, y def mod_inverse(a, m): g, x, y = extended_gcd(a, m) if g != 1: raise ValueError("Modular inverse does not exist") return x % m # Step 3: Generate RSA keys def generate_rsa_keys(bits): p = generate_prime(bits) q = generate_prime(bits) n = p * q phi_n = (p - 1) * (q - 1) while True: e = random.randint(2, phi_n) if math.gcd(e, phi_n) == 1: break d = mod_inverse(e, phi_n) return ((e, n), (d, n)) # Step 4: RSA encryption def rsa_encrypt(plaintext, public_key): e, n = public_key encrypted_msg = [pow(ord(char), e, n) for char in plaintext] return encrypted_msg # Step 5: RSA decryption def rsa_decrypt(encrypted_msg, private_key): d, n = private_key decrypted_msg = ''.join([chr(pow(char, d, n)) for char in encrypted_msg]) return decrypted_msg ``` ```

## Explanation

1. We begin by importing the necessary libraries: `random` for generating random numbers, and `math` for mathematical operations.
2. We define functions for RSA key generation, ensuring the secure generation of prime numbers and calculating the modular inverse for encryption and decryption.
3. Next, we generate RSA keys to create a public-private key pair.
4. With our custom `rsa_encrypt` and `rsa_decrypt` functions, we demonstrate how to encrypt and decrypt messages using the generated RSA keys.

## AES Encryption:

AES (Advanced Encryption Standard) is a symmetric encryption algorithm that employs the same key for both encryption and decryption. As part of our guide, we'll illustrate the AES encryption process using Python and the `PyCryptodome` library:

``````python # Step 1: Install the required library (if not already installed) # pip install pycryptodome # Step 2: Import necessary libraries from Crypto.Cipher import AES from Crypto.Random import get_random_bytes from Crypto.Util.Padding import pad, unpad # Step 3: AES encryption def aes_encrypt(plaintext, key): key = key[:16] # AES-128 requires a 16-byte key cipher = AES.new(key, AES.MODE_CBC, get_random_bytes(16)) ciphertext = cipher.encrypt(pad(plaintext.encode(), AES.block_size)) return ciphertext # Step 4: AES decryption def aes_decrypt(ciphertext, key): key = key[:16] # AES-128 requires a 16-byte key cipher = AES.new(key, AES.MODE_CBC, ciphertext[:16]) plaintext = unpad(cipher.decrypt(ciphertext[16:]), AES.block_size) return plaintext.decode() ``` ```

## Explanation:

1. To begin, we ensure the `pycryptodome` library is installed, allowing us to access AES functionality.
2. We import the necessary modules from the `Crypto` package, including `AES`, `get_random_bytes`, `pad`, and `unpad`.
3. Our `aes_encrypt` function demonstrates how to encrypt plaintext using AES with a specified key, providing a crucial layer of security.
4. For decryption, we present the `aes_decrypt` function, which utilizes the same key to decode the ciphertext back to its original form.

## Final Note:

We understand that encryption is a complex subject. While this guide provides you with fundamental insights and Python implementations, secure encryption implementation requires additional considerations beyond the provided code. In real-world scenarios, adopting established cryptographic libraries and best practices is essential.