This is a great talk, but it’s ignoring the real issue in that it would need to be “on-line”, which is not anywhere near possible. They sort of address that, but are talking about the cyphers themselves mostly.

I think we’ve reached the cusp where we can exchange new derivative keys on the fly per request without making too much of a dent in speed, but that comes with all kinds of tradeoffs on session length and convenience I suppose.