Re: [Bitcoin-development] New P2P commands for diagnostics, SPV clients

[Mike Hearn <mike@plan99.net>]

One thing that occurred to me recently is that it'd be useful if
filters could contain exact matches as well as Bloom filters.

Specifically I'm thinking of things like my bond network proposal
where some outputs may be marked as special using script fragments
like "BOND" <data or hash of data> 2DROP.

This would allow systems that are only interested in data and
transactions relevant to bonds to exact-filter the chain on that
marker, and then when a transaction is discovered, add the hash of
that transaction to a parallel Bloom filter, ensuring you can see any
transactions that connect to it.

The spec as provided by Jeff doesn't specify how filters are matched
against transactions. I propose the following algorithm:

For each TX:
- Check if the hash of the tx itself matches the filter
- For each input:
  - For each script data element check if it is found in the filter
  - Check if the COutPoint.hash value is in the filter (let's you
select txns that connect to arbitrary txns of interest)
- For each output
  - For each script data element check if it is found in the filter