file_encryption.py

"""This module provides functions to encrypt and decrypt strings."""

from cryptography.fernet import Fernet
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
from cryptography.hazmat.backends import default_backend
from base64 import urlsafe_b64encode
import string
import secrets
import os


def random_string(size):
    """Generate a random string of letters and digits."""
    letters = string.ascii_lowercase + string.ascii_uppercase + string.digits
    return "".join(secrets.choice(letters) for i in range(size))


generated_salt = os.environ.get("SALT", random_string(2048)).encode()


def generate_key_from_string(string_key):
    """Generate a key from a string."""
    # Derive a cryptographic key from the input string key
    kdf = PBKDF2HMAC(algorithm=hashes.SHA256(), length=32, salt=generated_salt, iterations=100000, backend=default_backend())
    key = urlsafe_b64encode(kdf.derive(string_key.encode()))
    return key


def encrypt_string(input_string, string_key):
    """Encrypt a string using a string key."""
    key = generate_key_from_string(string_key)
    fernet = Fernet(key)
    return fernet.encrypt(input_string.encode()).decode()


def decrypt_string(encrypted_string, string_key):
    """Decrypt a string using a string key."""
    key = generate_key_from_string(string_key)
    fernet = Fernet(key)
    return fernet.decrypt(encrypted_string.encode()).decode()