[noise] Clever UDP Keying

[Jason A. Donenfeld]

Hi folks,

With TCP, you can rekey after every packet if you want, because
delivery is guaranteed. Horrah!

With UDP, we don't have the same luxury. Packets even come out of
order. The best "obvious" solution is to rekey based on a timer.

The noise spec now relaxes the rekeying requirement to allow for
UDP-based usage, which is nice.

I'm wondering if anybody has any ideas of how to do something similar
to "rekeying after every packet" without reinventing some half-assed
TCP variant (adding ACK messages, etc), where the key mutates. That is
to say - is there some way in which packets coming out of order, or
not being delivered at all, can mutate a symmetric key in a useful
way? Has there been much research into interesting crypto systems that
would have this nice property? Anyone know of any papers I could read?

Thanks,
Jason