I have not seen an argument that these proposals scale to a key per
message. I'm not saying they don't; I'm saying that's not how people
seem to be thinking about the problem or writing software.
I don't think that's likely either, but assuming you had a specialized DNS
server that could handle the stream of key updates, I don't see any reason
to rule it out.
Regards,
John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet
for Dummies",
Information Superhighwayman wanna-be, http://iecc.com/johnl, Mayor
"I dropped the toothpaste", said Tom, crestfallenly.