Building a File Encrypter in Python with AES and PBKDF2

The article introduces a hands‑on tutorial that shifts focus from web development to software development, specifically exploring cryptography and information security using Python. It assumes readers have basic knowledge of Python or another object‑oriented language and are comfortable with the command line.

It explains the core concept of encryption: converting plaintext into ciphertext using a reversible process that requires a secret key. The tutorial chooses AES (Advanced Encryption Standard) in CBC mode and derives a 256‑bit key with PBKDF2.

Required tools include Python 3 and the pycryptodome library. Installation instructions are provided for Windows (via WSL), macOS (using Homebrew with brew install python3 ), and Linux. After setting up the environment, the user creates a file named crypto.py .

The script first imports necessary modules ( AES , PBKDF2 , get_random_bytes from Pycryptodome, and os ). It then defines an encrypt function that pads the plaintext, generates a random 16‑byte IV, creates an AES cipher object in CBC mode, and returns IV + ciphertext .

Next, an encrypt_file function reads a file, encrypts its contents with the previously defined function, writes the result to a new file with an .enc extension, and removes the original file.

A corresponding decrypt function extracts the IV from the first 16 bytes of the ciphertext, reconstructs the AES cipher, decrypts the remaining data, and strips padding. A decrypt_file function mirrors the file‑handling steps of its encryption counterpart.

Key generation is handled by a generate_key function that uses PBKDF2 with a user‑provided password and a fixed salt to produce a 32‑byte key. The tutorial notes that a fixed salt is insecure and should not be used in production.

Finally, a simple driver script demonstrates usage: it defines a secretfile variable, generates a key, encrypts the file, then decrypts it, printing status messages. The article warns that the code is for educational purposes only and should not be used to protect sensitive data without proper security reviews.

Overall, the tutorial provides a complete, runnable example of file encryption and decryption in Python, encouraging readers to experiment further with hashing, password verification, and stronger security practices.