[bitcoin-dev] BIP 158 Flexibility and Filter Size

[Matt Corallo <lf-lists@mattcorallo.com>]

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.

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.

Matt