XOR decryption

We have already considered how to provide XOR encryption in the previous chapter. But what about decryption?
Let's look at the following code:


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# Encoding function
def xor_encode(text, key):
    # Convert text and key to binary strings
    binary_text = ''.join(format(ord(char), '08b') for char in text)
    binary_key = ''.join(format(ord(char), '08b') for char in key)

    # Repeat the key to match the length of the text
    repeated_key = (binary_key * (len(binary_text) // len(binary_key) + 1))[:len(binary_text)]

    # XOR each bit of the text with the corresponding bit of the key
    encoded_text = ''.join(str(int(bit_text) ^ int(bit_key)) for bit_text, bit_key in zip(binary_text, repeated_key))

    return encoded_text
  
# Decoding function
def xor_decode(encoded_text, key):
    # Convert encoded text and key to binary strings
    binary_encoded_text = encoded_text
    binary_key = ''.join(format(ord(char), '08b') for char in key)

    # Repeat the key to match the length of the encoded text
    repeated_key = (binary_key * (len(binary_encoded_text) // len(binary_key) + 1))[:len(binary_encoded_text)]

    # XOR each bit of the encoded text with the corresponding bit of the key
    decoded_text = ''.join(str(int(bit_encoded) ^ int(bit_key)) for bit_encoded, bit_key in zip(binary_encoded_text, repeated_key))

    # Convert the binary string back to characters
    decoded_text = ''.join(chr(int(decoded_text[i:i+8], 2)) for i in range(0, len(decoded_text), 8))

    return decoded_text

# Example usage:
encoded_message = xor_encode("Hello, XOR Decoding!", "secretkey")

# XOR Decoding
decoded_message = xor_decode(encoded_message, "secretkey")

print(f"Encoded Message : {encoded_message}")
print(f"Decoded Message : {decoded_message}")

The decoding function is almost the same as encoding; the only difference is the existence of the additional line that decodes binary representation into the text format (line 28).

Everything was clear?

Section 3. Chapter 6