Re: [TLS] [ECH] Reverting the config ID change

[Eric Rescorla <[e-mail]>]

On Tue, Feb 16, 2021 at 3:01 PM Martin Thomson <[e-mail]> wrote:

> On Wed, Feb 17, 2021, at 08:31, Christopher Wood wrote:
> > That's true, but I'd personally prefer one tracking vector to two. This
> > structure also better aligns with other proposed use cases for HPKE
> > configurations. I also don't see an immediate need for flexibility in
> > this value given that there are extensions in ECHConfigContents already.
>
> I don't see the tracking angle as relevant here.  The only things that
> might matter is size, collision probability (for greasing), and
> consistency.  Size doesn't matter, because it's a handful of bytes at most;
> collisions matter little because the cost is a resource the server is
> prepared to spend anyway; consistency with something that can also change
> isn't worth much.
>
> The primary argument I would have in support of this is YAGNI.  The number
> of active keys should be much smaller than 256, and there's a slot for
> extensions should that need arise.
>

I don't find YAGNI that persuasive in this case. It's not significant extra
complexity to have this field bigger and it basically makes it impossible
to have any structure.

-Ekr