Re: Packet number encryption

["Fossati, Thomas (Nokia - GB/Cambridge)" <[e-mail]>]

On 03/02/2018, 02:31, "Jana Iyengar" <[e-mail]> wrote:
> A few points as I catch up on this thread. 
> 
> First, I'll remind folks that QUIC is an encrypted transport. I say
> this because the cost of this operation is trivial in the context of
> encrypting every packet. The cost is borne at the servers and not at
> middleboxes, so the additional crypto cost is basically trivial.

"QUIC is an encrypted transport" is bit vague a definition.  And it is
exactly that vagueness that we are discussing here, I think, that is:
deciding when grey becomes one of white or black.

Going back for a second to IoT: imagine using short header with no CID &
tiny payloads - e.g., the typical 2-4 bytes periodic sensor reading.  In
this case, PN encryption would increase the crypto compute per packet by
something around 50%, which can make a substantial difference on
low-power, battery operated devices.

This is a rather extreme case, but it serves to illustrate the point
that when moving in that greyish space, it makes sense to maybe allow
run-time choices instead of forcing a specific policy, which has the
potential to alienate an entire class of use cases, at design time.

Let endpoints negotiate the grey feature and make it black or white
depending on their cost-benefit judgement.

In particular, from a security/privacy perspective, PN encryption looks
entirely like a client decision.

And then there is the manageability issue that Roni and Piotr have
raised, which is very important, and should be weighted in the feature
selection process carefully.  It's not great for people sitting in NOC
rooms to have their toolboxes and expertise annihilated by a major
rollout at some big content provider.

Re: the ossification concern.  I'm am unable to assess the advantage PN
encryption would bring compared to Brian's approach of changing the wire
image frequently and have co-existing incompatible versions - mainly
because it's pretty difficult to tell now at what rate new QUIC versions
will be rolled out.

Cheers!