XOR Data Uncrypter

Building a custom XOR data decrypter in Python takes advantage of a fascinating cryptographic property: the XOR operation is its own inverse. This means that running the exact same function over encrypted data with the same secret key will instantly decrypt it back to its original form.

Because of this symmetry, a single Python script serves as both your encryptor and decrypter. Core Mechanics of XOR Decryption

The XOR operator (^ in Python) works at the bit level. If two bits are identical, it yields 0. If they are different, it yields 1. Encryption: Decryption: 1. Simple Single-Byte XOR Decrypter

If your data was encrypted using a single repeating character (e.g., 0xAA or K), you can use a basic generator expression.

def single_byte_xor(data: bytes, key: int) -> bytes: “”“Encrypts or decrypts data using a single-byte key.”“” return bytes([byte ^ key for byte in data]) # Example Usage encrypted_payload = b’F’ secret_byte = 0x66 # Decryption key decrypted_message = single_byte_xor(encrypted_payload, secret_byte) print(f”Decrypted: {decrypted_message.decode(‘utf-8’)}“) Use code with caution. 2. Multi-Byte (Repeating Key) XOR Decrypter

Most real-world XOR schemes use a multi-character string or dynamic byte-array as a key. To decrypt this, you need to loop through the data and cycle through the key dynamically. Python’s itertools.cycle handles this flawlessly without truncating your data.

from itertools import cycle def repeating_key_xor(data: bytes, key: bytes) -> bytes: “”“Decrypts or encrypts data using a multi-byte repeating key.”“” # cycle(key) automatically loops back to the start of the key return bytes([byte ^ key_byte for byte, key_byte in zip(data, cycle(key))]) # Example Usage cipher_data = b’‘ key_phrase = b”SECRET” plain_data = repeating_key_xor(cipher_data, key_phrase) print(f”Decrypted: {plain_data.decode(‘utf-8’)}“) Use code with caution. 3. Processing Entire Files

If you are dealing with malware analysis, game assets, or network packet dumps, you will want a decrypter that processes files safely using binary mode (‘rb’ and ‘wb’).

def decrypt_file(input_path: str, output_path: str, key: bytes): “”“Reads an encrypted file, applies XOR decryption, and saves the output.”“” try: with open(input_path, ‘rb’) as f: encrypted_data = f.read() # Re-use our multi-byte function decrypted_data = repeating_key_xor(encrypted_data, key) with open(output_path, ‘wb’) as f: f.write(decrypted_data) print(f”Successfully decrypted and saved to {output_path}“) except FileNotFoundError: print(“Error: The specified file could not be found.”) # Usage # decrypt_file(“locked_config.dat”, “config.json”, b”Pass123”) Use code with caution. Critical Security Trade-offs Python 3.6 File Decryption with XOR – Stack Overflow