xor.py

def xor_data(data: bytes, key: bytes) -> bytes:
    """XOR each byte of data with repeating key bytes."""
    return bytes([b ^ key[i % len(key)] for i, b in enumerate(data)])

# Hide file_a inside file_b
def hide_file(file_a, file_b, key, out_file):
    with open(file_a, "rb") as f1, open(file_b, "rb") as f2:
        data_a = f1.read()
        data_b = f2.read()

    key_bytes = key.encode()
    hidden = xor_data(data_a, key_bytes)

    # Combine: original B + XORed A
    with open(out_file, "wb") as out:
        out.write(data_b + b"\n---HIDDEN---\n" + hidden)

# Extract hidden A
def extract_file(out_file, key, extracted_file):
    with open(out_file, "rb") as f:
        combined = f.read()

    # Split on marker
    data_b, hidden = combined.split(b"\n---HIDDEN---\n")
    key_bytes = key.encode()
    data_a = xor_data(hidden, key_bytes)

    with open(extracted_file, "wb") as f:
        f.write(data_a)