[noise] 4 bytes leftover in nonce

[Jason A. Donenfeld]

Hi folks,

As you know, our nonce is 8 bytes, because 12 bytes is ambiguous and
hard to increment. We set 4 of those bytes to a zero. I've seen this
referred to as a "salt" in some places. I'm wondering if there are any
interesting uses of these 4 bytes - other than just being boring old
zero. Differing parallel streams using the same pair of keys?

Jason