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

From: Peter Todd <[email-masked]>
Date: Thu, 17 May 2018 11:43:15 -0400

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