Python Project - Encrypt and Decrypt files with Symmetric Encryption

Last update on September 16 2025 12:33:02 (UTC/GMT +8 hours)

File Encryption/Decryption: Create a program that encrypts and decrypts files.

Input values:

User interacts with the program by selecting files to encrypt or decrypt and providing encryption/decryption keys.

Output value:

Encrypted or decrypted versions of the selected files based on user input.

Example:

Input values:
1. Select a file to encrypt: "test.txt"
2. Enter the encryption key: "secretkey123"
Output value:
The program encrypts the file "test.txt" using the provided encryption key "secretkey123" and saves the encrypted version as "test_encrypted.txt".
Input values:
3. Select a file to decrypt: "test_encrypted.txt"
4. Enter the decryption key: "secretkey123"
Output value:
The program decrypts the file "test_encrypted.txt" using the provided decryption key "secretkey123" and saves the decrypted version as "document_decrypted.txt".

Solution: Using Fernet (Symmetric Encryption with Cryptography Library)

Code:

# Import necessary modules from cryptography library
from cryptography.fernet import Fernet

# Function to generate an encryption key and save it
def generate_key():
    key = Fernet.generate_key()  # Generate a new Fernet encryption key
    with open("secret.key", "wb") as key_file:  # Save the key to a file
        key_file.write(key)

# Function to load an existing encryption key from file
def load_key():
    return open("secret.key", "rb").read()  # Read and return the encryption key

# Function to encrypt a file using a provided key
def encrypt_file(file_path):
    key = load_key()  # Load the encryption key
    fernet = Fernet(key)  # Create a Fernet instance with the key
    
    # Read the file content
    with open(file_path, "rb") as file:
        file_data = file.read()
    
    # Encrypt the file data
    encrypted_data = fernet.encrypt(file_data)
    
    # Write the encrypted data to a new file
    with open(f"{file_path}_encrypted", "wb") as file:
        file.write(encrypted_data)

# Function to decrypt an encrypted file using the key
def decrypt_file(file_path):
    key = load_key()  # Load the encryption key
    fernet = Fernet(key)  # Create a Fernet instance with the key
    
    # Read the encrypted file content
    with open(file_path, "rb") as file:
        encrypted_data = file.read()
    
    # Decrypt the file data
    decrypted_data = fernet.decrypt(encrypted_data)
    
    # Write the decrypted data to a new file
    with open(f"{file_path}_decrypted", "wb") as file:
        file.write(decrypted_data)

# Example usage:
generate_key()  # Only run once to generate the key
encrypt_file("test.txt")  # Encrypt the file
decrypt_file("test.txt_encrypted")  # Decrypt the file

Explanation:

Generate Encryption Key: Creates a secure key using Fernet and saves it.
Load Encryption Key: Reads the key from file for encryption or decryption.
Encrypt File: Encrypts file content using Fernet with the loaded key.
Decrypt File: Decrypts the encrypted file with the same key.

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