xor
Returns a new array where every byte is xor-combined with the repeating key.
The key is applied cyclically: output index i is this[i] xor key[i % key.size]. The receiver is not modified. Applying the same key twice restores the original bytes. An empty receiver produces an empty array.
Return
a new array of the same size as the receiver.
Parameters
key
the key bytes to repeat over the input.
Throws
if key is empty.