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?