Re: [websec] Comments on draft-ietf-websec-key-pinning-06

[Chris Palmer <[e-mail]>]

If you haven't already, I'd urge everyone to take pcaps of a web
session to their bank or to their web mail provider or whatever. I
think you'll quickly see that even a large HPKP header, say 500 bytes,
is not going to be the thing that makes web traffic bloated.
(Sometimes, the certificate chains themselves outweigh the pins — and
that traffic occurs before the crucial point of widening the TCP
window! Whereas HTTP headers most likely occur afterward.)

Also, at one point somebody raised an idea of saying you could pin to
a set of keys — say, Symantec or StartCom's issuing certs — with a
single directive. Something like:

    Public-Key-Pins: max-age=...; pin-set: symantec; includeSubDomains

There'd need to be some kind of registry for the names of sets, of
course, which is complicated. And how do UAs learn of updates to the
sets, and so on. It's a nice idea that would improve on-the-wire size
in bytes, and also enable web application providers to pin more
easily. If there is demand, perhaps we could create such an extension
to HPKP/TACK/et c. But I don't think it should be a blocker for this
I-D.