Insecure encryption algorithm - TripleDES
Need
Secure encryption algorithm for data protection
Context
- Usage of Python 3 for writing and executing Python code
- Usage of pycryptodome for cryptographic operations in Python
Description
Non compliant code
from Crypto.Cipher import DES3
from Crypto import Random
key = b'Sixteen byte key'
iv = Random.new().read(DES3.block_size) # ensure this is unique for each message
cipher = DES3.new(key, DES3.MODE_ECB, iv)
plaintext = b'Attack at dawn'
msg = cipher.iv + cipher.encrypt(plaintext)
In this Python code snippet, we are using the pycrypto library to create an instance of the DES3 (Triple DES) cipher in ECB (Electronic Code Book) mode.
The key is a 16-byte string, and the initialization vector (iv) is randomly generated for each new message. The plaintext message 'Attack at dawn' is then encrypted using this cipher.
The vulnerability here lies in the use of both the Triple DES encryption algorithm and the ECB mode.
Triple DES is considered insecure because it is susceptible to meet-in-the-middle and key-reuse attacks. Moreover, it has a relatively small block size (64 bits), which makes it less secure for encrypting large amounts of data.
The ECB mode is also insecure because it encrypts identical plaintext blocks into identical ciphertext blocks, making it vulnerable to pattern analysis. Furthermore, it does not use an initialization vector, which means that the same plaintext will always result in the same ciphertext when encrypted with the same key.
In summary, the use of Triple DES in ECB mode in this code makes it vulnerable to several types of cryptographic attacks. To fix this, we should switch to a more secure encryption algorithm (like AES) and a more secure mode of operation (like CBC or GCM).
Steps
- Replace the TripleDES (DES3) encryption algorithm with a more secure one such as AES (Advanced Encryption Standard).
- Avoid using ECB (Electronic Code Book) mode as it is insecure. Instead, use a mode that provides confidentiality and authenticity, such as GCM (Galois/Counter Mode).
- Ensure that the initialization vector (IV) is unique for each encryption operation. It should be randomly generated and not reused.
- Consider using a library that provides high-level encryption functionalities, such as PyNaCl or cryptography.io, to avoid common pitfalls in cryptographic code.
Compliant code
from Crypto.Cipher import AES
from Crypto.Random import get_random_bytes
key = get_random_bytes(16)
cipher = AES.new(key, AES.MODE_GCM)
plaintext = b'Attack at dawn'
nonce = cipher.nonce
ciphertext, tag = cipher.encrypt_and_digest(plaintext)
msg = nonce + ciphertext + tag
The above code fixes the vulnerability by replacing the insecure TripleDES (DES3) encryption algorithm with the more secure AES (Advanced Encryption Standard).
AES is currently the most secure symmetric encryption algorithm and is widely used in many security systems worldwide. It is also approved by the National Institute of Standards and Technology (NIST) in the United States.
The code also replaces the insecure ECB (Electronic Code Book) mode with the GCM (Galois/Counter Mode). GCM provides both confidentiality and authenticity, making it a better choice for most encryption tasks.
The key is generated using the get_random_bytes function, which generates a random 16-byte key. This key is used to create a new AES cipher object in GCM mode.
The plaintext message 'Attack at dawn' is then encrypted using the encrypt_and_digest method of the cipher object. This method returns the ciphertext and a tag that can be used to verify the integrity of the message during decryption.
The nonce (number used once), ciphertext, and tag are concatenated to form the final encrypted message. The nonce is included in the message because it is needed for decryption and must be unique for each message encrypted with the same key.
This code ensures that the encryption process is secure by using a strong encryption algorithm, a secure mode of operation, and a unique nonce for each message.