Re: [bitcoindev] Relax OP_RETURN standardness restrictions

[Peter Todd <pete@petertodd.org>]

[-- Attachment #1: Type: text/plain, Size: 2108 bytes --]

On Thu, Apr 17, 2025 at 06:52:34PM +0000, 'Antoine Poinsot' via Bitcoin Development Mailing List wrote:
> Hi,
> 
> Standardness rules exist for 3 mains reasons: mitigate DoS vectors, provide upgrade hooks, or as a nudge to deter some usages.
> 
> Bitcoin Core will by default only relay and mine transactions with at most a single OP_RETURN output, with a scriptPubKey no larger than 83 bytes. This standardness rule falls into the third category: it aims to mildly deter data storage while still allowing a less harmful alternative than using non-provably-unspendable outputs.
> 
> Developers are now designing constructions that work around these limitations. An example is Clementine, the recently-announced Citrea bridge, which uses unspendable Taproot outputs to store data in its "WatchtowerChallenge" transaction due to the standardness restrictions on the size of OP_RETURNs[^0]. Meanwhile, we have witnessed in recent years that the nudge is ineffective to deter storing data onchain.
> 
> Since the restrictions on the usage of OP_RETURN outputs encourage harmful practices while being ineffective in deterring unwanted usage, i propose to drop them. I suggest to start by lifting the restriction on the size of the scriptPubKey for OP_RETURN outputs, as a first minimal step to stop encouraging harmful behaviour, and to then proceed to lift the restriction on the number of OP_RETURN outputs per transactions.

I would suggest removing both limits at the same time.

While multiple OP_Return outputs are more expensive than a single one
for the same amount of total data. In some cases they're necessary for
technical reasons, e.g. if signing with SIGHASH_SINGLE.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org

-- 
You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group.
To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/aASzwkFfGFBYudK_%40petertodd.org.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]