Re: [Ppm] Interim topic: Shall DAP support heavy hitters?

[Christopher Patton <[e-mail]>]

Hi aggregators,

Just wanted to remind folks planning to attend the interim on Monday that
we're hoping to reach consensus on the following questions:
https://docs.google.com/document/d/1ZjXz-1kGsTDf2Vn2u-fwYqR8BSc3tOYlELVHAYvAfjk/edit#heading=h.c05ztkgnagl

I've also asked the chairs if we can do hums, just to make sure we hear
from everyone who cares about the heavy hitters use case.

Thanks,
Chris P.

On Thu, Apr 11, 2024 at 3:37 PM Christopher Patton <[e-mail]>
wrote:

> Hi everyone,
>
> I've prototyped most of the changes for Proposal #1 in Daphne:
> https://github.com/cloudflare/daphne/pull/575
>
> Lots of this would be reusable for #2. I hope this gives folks a sense of
> the scope of changes required for supporting heavy hitters.
>
> Chris P.
>
> On Mon, Apr 8, 2024 at 4:18 PM Christopher Patton <[e-mail]>
> wrote:
>
>> Hi folks,
>>
>> As noted at IETF 118, there are a number of issues for the DAP spec
>> related to supporting heavy hitters via Poplar1:
>>
>> https://datatracker.ietf.org/meeting/118/materials/slides-118-ppm-dap-open-issues
>>
>> We'd like to spend a significant chunk of time during the interim on
>> resolving these issues. To that end, Tim G. and I have been leading a small
>> design team over the last couple of months towards identifying a set
>> protocol changes to support this important use case. We need your help
>> deciding between three different options:
>>
>> - Proposal #0: Don't support heavy hitters in DAP (punt to a future
>> protocol spec)
>> - Proposal #1: Support heavy hitters with minimal changes to DAP
>> - Proposal #2: Support heavy hitters, but amend the collection
>> sub-protocol to minimize the amount of information revealed to the Collector
>>
>> Each proposal is detailed in the following google doc:
>>
>> https://docs.google.com/document/d/1ZjXz-1kGsTDf2Vn2u-fwYqR8BSc3tOYlELVHAYvAfjk/edit?usp=sharing
>>
>> It would be helpful if folks could spend some time ahead of the interim
>> (22 April, two weeks from now) digesting these options, providing feedback,
>> and figuring out what information you need, if any, to form an opinion. My
>> hope is that we'll be prepared to make a decision during the interim on the
>> questions enumerated in Section 6.
>>
>> Relatedly: If we decide to support heavy hitters, then we'll also need to
>> decide how to deal with a class of attacks against DAP/Poplar1 articulated
>> by Simon Friedberger and Phillipp Schoppmann. We call these "steering
>> attacks", as they exploit the fact that the attacker in our threat model
>> has partial control of the protocol execution that is not considered the
>> original Poplar paper (https://ia.cr/2021/017). There are a few
>> mitigations in the google doc that we'd like folks to mull over.
>>
>> I'm looking forward to seeing folks online in a couple of weeks.
>>
>> Thanks,
>> Chris P.
>>
>