[CFRG] Re: Should we spell out the star topology for VDAFs?

[Christopher Patton <[e-mail]>]

Here is a PR for closing the issue by just sketching the star topology:
https://github.com/cfrg/draft-irtf-cfrg-vdaf/pull/390

Best,
Chris P.

On Fri, Aug 2, 2024 at 5:26 PM Christopher Patton <[e-mail]>
wrote:

> Hi PPM+CFRG,
>
> I'd like to get some feedback on what to do about this issue for the VDAF
> draft:
> https://github.com/cfrg/draft-irtf-cfrg-vdaf/issues/261
>
> Prior to DAP draft 05, we envisioned a "star topology" in which there is a
> single leader and any number of helpers. The idea was that for each round
> of preparation, the leader would broadcast the prep message to each of the
> helpers: each helper would respond with its prep share for the next round,
> which the leader would use to compute the prep message for the next round,
> and so on. In draft 05 we decided to specialize the protocol for a single
> leader and helper and adopt the ping-pong topology [1], which requires
> fewer round trips over the network to finish.
>
> In theory, a future specification could execute a VDAF in a star topology,
> so it may be useful to spell this out. Note however that not all VDAFs
> support more than two aggregators: Prio3 does, but Poplar1 doesn't.
>
> The VDAF draft spells out ping ponging in full detail. This is necessary
> because the DAP draft consumes this API directly. Do folks think we should
> spell out the star topology in the same level of detail?
>
> Since we don't currently have a use case for it, I don't think it's
> necessary to spell out in full detail. I suggest we just sketch it instead.
>
> Thanks!
> Chris P.
>
> [1]
> https://www.ietf.org/archive/id/draft-irtf-cfrg-vdaf-10.html#section-5.8
>