Subject: Re: [bitcoin-dev] Bitcoin Transaction Relay over Nostr

From: Joost Jager <[email-masked]>
Date: Tue, 30 May 2023 14:30:51 +0200

Hi David,

> A block template is an ordered list of raw transactions that can all be
> included in the next block (with some space reserved for a coinbase
> transaction).  A full node can validate those transactions and calculate
> how much fee they pay.  A Nostr relay can simply relay almost[1] any
> template that pays more fees than the previous best template it saw for
> the next block.  That can be more flexible than the current
> implementation of submitblock with package relay which still enforces a
> lot of the rules that helps keep a regular relay node safe from DoS and
> a miner node able to select mineable transactions quickly.
>

Interesting idea! This would also make it easy for external services to try
to do the best possible block building using advanced algorithms. Miners
would just select the best template available from various sources
including nostr.

> A weak block is a block whose header doesn't quite hash to low enough of
> a value to be included on the chain.  It still takes an extraordinary
> amount of hashrate to produce, so it's inherently DoS resistant.  If
> miners are producing block that include transactions not seen by typical
> relay nodes, that can reduce the efficiency and effectiveness of BIP152
> compact block relay, which hurts the profitability of miners of custom
> blocks.  To compensate, miners could relay weak blocks through Nostr to
> full nodes and other miners so that they could quickly relay and accept
> complete blocks that later included the same custom transactions.  This
> would also help fee estimation and provide valuable insights to those
> trying to get their transactions included into the next block.
>

I believe this would be useful right away, wouldn't it? Looking at
mempool.space's block audit, there are definitely blocks that have a
"surprising" content and might take long to download.

The anti-dos measures that you describe for both weak blocks and block
templates seem very robust, but they would require a more intelligent nostr
relay to enforce. Not sure if it is still allowed to call it nostr at that
point. Perhaps it becomes more of a specialised bitcoin relay. btcstr -
"bitcoin stuff transmitted by relays".

Regarding size, the block template and weak block could both be sent in
> BIP152 compact block format as a diff against the expected contents of a
> typical node, allowing Alice to send just a small amount of additional
> data for relay over what she'd have to send anyway for each transaction
> in a package.  (Although it's quite possible that BetterHash or Stratum
> v2 have even better solutions, possibly already implemented.)
>

Sounds like a great way to repurpose what already exists to reduce resource
usage for these additional message types.

> If nothing else, I think Nostr could provide an interesting playground
> for experimenting with various relay and mining ideas we've talked about
> for years, so thanks again for working on this!
>

I think so too! The main question on my mind though is how to actually make
this work. There is a bit of a chicken-egg problem here with users and
miners possibly waiting for each other to adopt.

Joost