Subject: Re: [bitcoin-dev] BIP 158 Flexibility and Filter Size

From: Riccardo Casatta <[email-masked]>
Date: Mon, 4 Jun 2018 10:42:10 +0200

I was wondering why this multi-layer multi-block filter proposal isn't
getting any comment,
is it because not asking all filters is leaking information?

Thanks

Il giorno ven 18 mag 2018 alle ore 08:29 Karl-Johan Alm via bitcoin-dev <
[email-masked]> ha scritto:

> On Fri, May 18, 2018 at 12:25 AM, Matt Corallo via bitcoin-dev
> <[email-masked]> wrote:
> > In general, I'm concerned about the size of the filters making existing
> > SPV clients less willing to adopt BIP 158 instead of the existing bloom
> > filter garbage and would like to see a further exploration of ways to
> > split out filters to make them less bandwidth intensive. Some further
> > ideas we should probably play with before finalizing moving forward is
> > providing filters for certain script templates, eg being able to only
> > get outputs that are segwit version X or other similar ideas.
>
> There is also the idea of multi-block filters. The idea is that light
> clients would download a pair of filters for blocks X..X+255 and
> X+256..X+511, check if they have any matches and then grab pairs for
> any that matched, e.g. X..X+127 & X+128..X+255 if left matched, and
> iterate down until it ran out of hits-in-a-row or it got down to
> single-block level.
>
> This has an added benefit where you can accept a slightly higher false
> positive rate for bigger ranges, because the probability of a specific
> entry having a false positive in each filter is (empirically speaking)
> independent. I.e. with a FP probability of 1% in the 256 range block
> and a FP probability of 0.1% in the 128 range block would mean the
> probability is actually 0.001%.
>
> Wrote about this here: https://bc-2.jp/bfd-profile.pdf (but the filter
> type is different in my experiments)
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-- 
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>