Instructions: Enter an integer less than 256 in the top textfield labeled "Key." Enter a plaintext sentence in the textfield labeled "Plaintext" then hit return. The key is used to scramble the plaintext by xor-ing with all its bytes. The scrambled result is shown in the textfield labeled "Ciphertext." The key is used again in exactly the same way to unscramble the ciphertext. The result is shown in the textfield labeled "Decrypted." What is the major weakness to this approach to cryptography?