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

From: Matt Corallo <[email-masked]>
Date: Thu, 17 May 2018 15:46:18 +0000

(1) can be accomplished by filtering for the set of outputs in the transaction you created. I agree (2) would ideally be done to avoid issues with a copied wallet (theft or not), but I am worried about the size of the filters themselves, not just the size of the blocks downloaded after a match.

On May 17, 2018 3:43:15 PM UTC, Peter Todd <[email-masked]> wrote:
>On Thu, May 17, 2018 at 11:25:12AM -0400, Matt Corallo via bitcoin-dev
>wrote:
>> BIP 158 currently includes the following in the "basic" filter: 1)
>> txids, 2) output scripts, 3) input prevouts.
>> 
>> I believe (1) could be skipped entirely - there is almost no reason
>why
>> you'd not be able to filter for, eg, the set of output scripts in a
>> transaction you know about and (2) and (3) may want to be split out -
>> many wallets may wish to just find transactions paying to them, as
>> transactions spending from their outputs should generally be things
>> they've created.
>
>So I think we have two cases where wallets want to find txs spending
>from their
>outputs:
>
>1) Waiting for a confirmation
>2) Detecting theft
>
>The former can be turned off once there are no expected unconfirmed
>transactions.
>
>As for the latter, this is probably a valuable thing for wallets to do.
>Modulo
>reorgs, reducing the frequency that you check for stolen funds doesn't
>decrease
>total bandwidth cost - it's one filter match per block regardless - but
>perhaps
>the real-world bandwidth cost can be reduced by, say, waiting for a
>wifi
>connection rather than using cellular data.
>
>-- 
>https://petertodd.org 'peter'[:-1]@petertodd.org